What term can be used for an adult, especially a man, who is in his forties and still behaves like a teenager, shunning responsibilities typical of mature people, preferring to enjoy himself?

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    The definition is what you have just supplied yourself. What you are looking for is the word, not its definition.
    – RegDwigнt
    Commented May 11, 2014 at 13:57
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    Note that this is not necessarily immaturity; it may simply be that he doesn't accept the same definition of maturity -- or the same constraints upon it -- that you do. Different people have different priorities.
    – keshlam
    Commented May 11, 2014 at 23:39
  • Once I was 18, my dad always called me "a dolt".
    – Thanatos
    Commented May 12, 2014 at 1:10
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    @keshlam Differing opinions should not be used as a benchmark for society. Some people truly believe killing others is fine. Do we pass it off and say "everyone is entitled to their opinions"? A person might not see themselves as immature, but if they behave that way, then they are.
    – Möoz
    Commented May 13, 2014 at 2:16
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    @BorhanMooz: Granted. But -- for example -- not everyone feels a need to raise children, or to own their own house, or to hit other benchmarks on the usual default description of maturity. There are certainly people who are more or less mature than others their age. But I think it's necessary to warn that the existence of a single word does not necessarily mean it's the right word for a particular individual, and that shunning "typical responsibilities" is not always good evidence of immaturity.
    – keshlam
    Commented May 13, 2014 at 3:00

15 Answers 15


I would just call such a person immature, defined by The American Heritage Dictionary as:

adj. Marked by or suggesting a lack of normal maturity: silly, immature behavior.

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    Sometimes the most obvious is the best. Commented May 12, 2014 at 1:05
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    It's interesting that there's really no word (noun) in English for this present-day phenomenon. (Culture is loaded with references to it - eg the movie "Failure to launch".) As Elian notes in French there's a slang term, and I believe there are many, many words in Japanese relating to this phenomenon (since it's the central problem in Japan's aging society of today).
    – Fattie
    Commented May 12, 2014 at 6:22
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    Simply google on failure to launch phenomenon for a number of ideas here. twixters, boomerangs, etc. Also regarding in foreign languages, apparently "In Italy, the high percentages of young adult men at home is referred to as the mammoni or mammismo phenomenon..."
    – Fattie
    Commented May 12, 2014 at 6:29
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    @JoeBlow the italian reference roughly translates to "sucker" - not as in "stupid" but rather as someone who is sucking on their parent's tit; as in "suckling".
    – Joum
    Commented May 12, 2014 at 17:05
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    In Italian the best term is a neologism, bamboccione, but also vitellone (from F. Fellini's movie) and mammone (mama's big boy). Commented May 13, 2014 at 23:39

Perhaps man-child, Peter Pan or perpetual teenager.

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    man-child is the one that I've heard most often.
    – qdjm
    Commented May 11, 2014 at 13:08
  • Peter Pan doesn't make sense here to me. Commented May 11, 2014 at 14:50
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    @RyeɃreḁd: See en.wikipedia.org/wiki/Puer_aeternus#Peter_Pan_syndrome
    – Erik Kowal
    Commented May 11, 2014 at 17:49
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    @qdjm: Note that man-child is also used, especially by US sports commentators, in an opposite way: to refer to a very talented young male athlete. Example. In this case, the suggestion is that although the athlete is chronologically a child, his skills are those of a fully grown man. Commented May 12, 2014 at 16:16

I do not think immature is the correct word, as maturity is defined by sociocultural norms. I think the word you're looking for is simply childish, because that describes behavior appropriate for a child (which is generally accepted to be someone who hasn't hit puberty).

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    It's important to note the difference in connotation between childish and childlike.
    – TRiG
    Commented May 12, 2014 at 14:45

Adulthood and Adolescence as States of Mind

What you are describing may be best characterized as someone who is a “late-stage” or “age-inappropriate” adolescent. An adolescent is neither a child nor an adult, but has one foot planted in each of those two worlds. Only once the former gives way to the latter does a person cease to be an adolescent.

That’s because when speaking not legally or biologically, but rather behaviorally and socially, adolescence is a state of mind. It’s a mental condition, a particular way of looking at oneself, one’s fellows, and one’s world.

As a social condition, adolescence persists until the individual lays aside the carefree world of the child. Only then can they take up the mantle of an actual adult with all its concomitant responsibilities.

There is no fixed time for this to occur; it may be early or it may be late, and it may not even be permanent.

  • Some few do this by age 14 or 15 when they marry, start families, and move into a home of their own, a practice far more common in earlier eras than today in the developed world.

  • Others delay until their 20s or 30s, or increasingly now in modern society, even into their 40s.

  • And some there are who forever remain adolescents until they at last die of old age.

A relevant quote from literature

The great American author Gene Wolfe frequently writes of these differences between children and adults, and of that “feet in both camps” world which adolescents for a time inhabit. Perhaps his clearest statement in this area is the following quotation:

Adolescents are simply those people who haven’t as yet chosen between childhood and adulthood. For as long as anyone tries to hold on to the advantages of childhood — the freedom from responsibility, principally — while seeking to lay claim to the best parts of adulthood, such as independence, he is an adolescent. [. . .] Eventually most people choose to be adults, or are forced into it. A very few retreat into childhood and never leave it again. A large number remain adolescents for life.

A person who per your description is “behaving like a teenager” is an adolescent, no matter whether they are 11 years old or 21 — or 51, 71, or 91.

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    Is that not a logical contradiction? That most people choose to be adults or are forced into it, yet a large number remain adolescents. I guess it's possible, but sounds strange.
    – Celeritas
    Commented May 12, 2014 at 23:54

Consider using one of these to describe such behavior:

  • childish
  • sophomoric

You can call him an infantile person.



  1. of or pertaining to a child or to childhood.
  2. childishly foolish, immature or trivial.

I'll concede this answer lacks some of what you're after - i) it's gender independent, ii) I typically associate the term with the behavior (the verb it's applied to is puerile) and not the person/object (in which case the noun it's applied to would be puerile).

Based on the question though, you may not even be after a word associated with immaturity. For example, "preferring to enjoy" oneself might be better described by hedonistic, and for "shunning responsibilities" simply irresponsible.

I guess if one were feeling particularly mean, a puerile, hedonistic, irresponsible adult.

  • Wow, that's a very good word for this, but I've never even seen it before...
    – Mdev
    Commented May 14, 2014 at 8:00

Do you mean a nonadult? That's the best thing I can think of. You can also call this person a peter pan, since he/she doesn't want to grow up.

  • I like this answer. "He was such a non-adult, eternally engrossed in his online games and trading collectables." It works, ya know? Commented May 12, 2014 at 11:56
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    I disagree; saying non-adult is oxymoronic because by definition (he is 40 years old) he is an adult. So he literally can't be a non-adult.
    – TylerH
    Commented May 14, 2014 at 0:13
  • But, methaphorically, you can use the term "non-adult", as you can describe him as a peter pan Commented May 14, 2014 at 0:16

From a medical/psychiatric view point, such a person may have a borderline adult personality disorder.

  • What is "borderline adult personality disorder"? A google search turns up only this answer. Commented May 13, 2014 at 18:14
  • @TrevorWilson I believe it's just borderline personality disorder with the age explicit in the name.
    – Mdev
    Commented May 14, 2014 at 7:59
  • Borderline personality disorder is much more than immaturity.Think Glenn Close in Fatal Attraction.
    – GMB
    Commented May 16, 2014 at 3:23

I would normally call that person a big baby.

My grandmother still calls me juvenile.

  • A big baby is someone who is easily upset by petty matters, or who takes offence ridiculously easily. That's one form of immaturity, yes, but I don't think it's a complete answer to the question.
    – TRiG
    Commented May 12, 2014 at 14:46

A man in his 40s who acts as if he were still a teenager? I have an expression for a "man" who has never grown up.

I'd call him a boy because he acts as a child.

child: an immature or irresponsible person

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    At some level, this very much reminds one of that ancient parable that we in English have come to call The Fable of the Ants and Grasshopper. See also the lupine quote I give in my answer for a more direct expression of this.
    – tchrist
    Commented May 11, 2014 at 21:04
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    @Mari-LouA There is a difference between being 'childlike' and being 'childish'. The latter usually implies immaturity and shunning of responsibility while the former doesn't. An adult can be childlike in that he or she feels young at heart, is trusting and somewhat naive, or has hobbies that are more enjoyed by the younger crowd. This doesn't necessarily mean the said person is irresponsible or temperamental like the stereotypical teenager. Commented May 12, 2014 at 3:21
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    Mari - you rock, thanks. If you were 17 I'd phone you up to go to a discotheque in my red convertible since I have no job ;-) (BTW I think what you describe in your post is more the "playboy idiot" type than the "Mammoni" type. I believe, possibly, the OP was asking more about the "Mammoni" type. As I mentioned above I believe in Japan in particular there are many words for the "Mammoni" phenomenon, since it is a huge socio-economic problem for that country; no children.)
    – Fattie
    Commented May 12, 2014 at 7:34
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    PlayBOY exactly :) A neologistic term might be "middle-aged kid/boy".
    – Mari-Lou A
    Commented May 12, 2014 at 7:37
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    Mari-Lou: there is a common term used in the media in the US and that is Man-child:...also to describe for a man that is physically an adult, but mentally/emotionally immature.. Many of Judd Apatow's movies are described where the protagonist is a 'manchild' someone who is middlea-ged and in middle-aged situations, but acts with the mentality of a teenager.
    – Mitch
    Commented May 12, 2014 at 13:50

This is probably not always fair or applicable to specific instances, but often such ones are called bachelors or playboys.


In France, we would call that kind of person "adulescent."

Consider "kidult and "adultescent."

adultescent: a young adult or middle-aged person that has interests, traits, etc., that are usually associated with teenagers.

kidult: an adult who is interested in forms of entertainment such as video games, TV shows, etc. that are intended for children.

In the way of adjectives, "adolescent" sounds like a good fit.

adolescent: emotionally or intellectually immature.

  • Indeed so, for no road leads out of adolescence save by way of adoloration.
    – tchrist
    Commented May 11, 2014 at 20:05

I call that person "unfledged".


I would call such a person a free spirit or wise man.

“Woe to the downpressors,” I would say.

  • What is a downpressor?
    – tchrist
    Commented May 12, 2014 at 23:04
  • @tchrist I could be wrong, but I believe a downpressor is an old, old wooden ship. Commented May 12, 2014 at 23:13
  • @tchrist - for downpressor google Peter Tosh
    – paulkayuk
    Commented May 14, 2014 at 11:48