For example, a computer security expert can be an expert and making a basic mistake, perhaps unrelated to his personality but highly relevant to his field of expertise and a mistake that just about anybody could do but just because he is a security expert he especially should not have done it.

I don't mean stupid mistake or stupid error but I mean contradictory and almost similar to a double-standard.

Jeff teaches English but he couldn't spell "occurrence".

Or for example

George is a professional Microsoft Windows programmer but he doesn't know what alt+tab does.


Henry is a surgeon but he cut himself shaving.

I don't necessarily mean something like a police officer who himself is corrupt or a judge who is corrupt because those are not accidents or mistakes but deliberate.

Albert Einstein was a genius but couldn't remember his own address and entered the wrong house when going home.

(Perhaps the above Einstein example is not a great example because scientist could be absent-minded.)

I mean more like actually mistakenly missing the basics of your own speciality or making a human error that anybody else could do except you because you are supposed to be the specialist.

I think the classic example could be Bill Gates trying to show how good Microsoft Windows is and it crashes.

Or a news anchor, who should be a specialist in not making a word mistake, actually makes a word mistake.

Or a judge or an attorney, who should be experts in law and rights, wouldn't know something trivial about law and right e.g. unknowingly about that blackmailing is a crime.

I almost made such a mistake myself. I was an IT specialist and computer technician at a client's office and their boss was teaching himself the basics of programming and asking me about something basic. I actually got it right but I was not completely certain about something basic while actually being able to solve complicated and advanced problems for them.


10 Answers 10


Such mistakes are bloopers.


blooper NOUN
North American informal
1 An embarrassing error

‘Home cooks perhaps identified with Mrs. Child, who, though she clearly knew her sauces and soufflés, also committed bloopers on camera.’

  • 5
    Blooper, in this sense, is almost completely confined to broadcast media.
    – Phil Sweet
    Jan 13, 2017 at 16:03
  • 1
    I think this is the word that gave me the strong intuition that there was a word. Jan 13, 2017 at 16:46
  • 2
    A blooper is an embarrassing error, but more due to carelessness than lack of knowledge or forgetfulness, which I think does not satisfy the OP requirements as stated, "I don't mean stupid mistake or stupid error". This word only seems to fit the Bill Gates and news anchor examples.
    – JPhil
    Jan 13, 2017 at 22:36
  • 1
    Another possibility, surprisingly not mentioned yet, is clunker.
    – Fattie
    Jan 14, 2017 at 12:53
  • 2
    I really don't see bloopers as amateur mistakes. They are almost always humorous mistakes unrelated to the actual subject. Examples of bloopers include someone sneezing in the middle of a dramatic dialog, a dog wandering into the scene, someone tripping and falling. etc. None of these really imply an expert making a mistake that only an amateur would be expected to make.
    – barbecue
    Jan 14, 2017 at 18:54

Not a single word, but one could call this a rookie mistake.

An example is "Trump's Trade Chief Makes a Rookie Mistake".

The Cato Institute’s Dan Ikenson recently took Navarro to task for his views on trade. Ikenson says Navarro is making an elementary error when he writes:

When net exports are negative, that is, when a country runs a trade deficit by importing more than it exports, this subtracts from growth.

It’s definitely not true that trade deficits always subtract from growth.

  • 8
    Although it would be a rookie mistake, it doesn't really encapsulate the fact that it was an expert's mistake in their field of expertise.
    – Hank
    Jan 13, 2017 at 15:28
  • 3
    @Hank Who else is capable of acting rookie-ish and it be a mistake?
    – Phil Sweet
    Jan 13, 2017 at 15:47
  • 10
    Rookies make rookie mistakes. Intermediates make rookie mistakes. Everyone can make a rookie mistake. I just don't think that rookie mistake automatically implies that an expert made it.
    – Hank
    Jan 13, 2017 at 15:47
  • 11
    Actually, I think if the mistake were to have been made by a "rookie" you wouldn't be likely to mention it (just as there's no reason to describe a basic mistake made by an actual schoolboy as a *schoolboy error"). So I think this is a good answer. Jan 13, 2017 at 15:48
  • 2
    When a seasoned professional does something that would be expected of a rookie, you say "Dan, that was a rookie mistake, what the hell happened?" It does have a connotation of being unexpected or surprising for the person its applied to. If the person making the mistake is in fact a rookie, then there's nothing surprising or unexpected about them making such mistakes, so no reason to specifically point it out.
    – barbecue
    Jan 14, 2017 at 18:58

Consider "lapse", which is defined by oxforddictionaries.com as

A brief or temporary failure of concentration, memory, or judgement

This perhaps applies best to the "surgeon who cuts himself shaving" example. For the other two examples, in which the expert lacks one piece of basic knowledge in his or her chosen field, consider "blind spot", this sense of which is defined by oxforddictionaries.com as

An area in which a person lacks understanding [...]

  • Yep; only saw this after I commented. Jan 14, 2017 at 14:18


A careless or stupid mistake.

  • 4
    Yes! This is a commonly used adjective to describe a poor choice of move made by a chess (grand)master.
    – Bohemian
    Jan 13, 2017 at 23:36
  • This is a good one too
    – Carly
    Jul 23, 2019 at 15:35

I like a lot of the answers here, but thought I'd throw yet another one into the mix:


  1. to perform poorly; blunder; bungle:

He flubbed the last shot and lost the match.

(Quote from Dictionary.com)

(Mostly I just like saying the word...)

  • I grew up in Chicago, and for the first 40 years of my life, we called the baseball team, the Flubs. Nor so much anymore ...
    – Stu W
    Jan 13, 2017 at 21:20

I would suggest a clanger.

It can mean an obvious, absurd or embarrassing mistake.

A 'professional clanger'.


That's a schoolboy error. — ODO

A very basic or foolish mistake. British, informal

Example sentences:

‘It was painful to watch, even more painful to hear the Doncaster fans laughing at York's schoolboy errors.’

‘Accusing respected clergymen of lying was a political schoolboy error.’

‘But he was judged a fool guilty of schoolboy errors when estimating 100,000 civilian deaths since the March 2003 US-UK invasion of Iraq.’

‘The company will be at pains not to let this type of embarrassing schoolboy error happen again.’

See also: Origins of "schoolboy error"


A less popular phrase similar to the excellent "rookie mistake" answer is a greenhorn mistake. A greenhorn is a person who is inexperienced or a newcomer to an area, and it's expected that such a person may make mistakes or not understand basics. When an experienced or professional person makes the same error, it's surprising and unusual. In such a case they can be described as making a greenhorn mistake. Qualifying the mistake with this word suggests that it's unusual or unexpected, whereas a truly inexperienced person would be expected to make such mistakes.

An example of this usage can be found here, describing a respected athlete making a mistake that is surprising for her level of experience and skill.


I've heard people say that they've made a boo-boo. (If it's hyphonated, doesn it count as one word?)

  • 2
    IMHO "boo boo" is a term used to trivialize the severity of an error, not related to the experience of the one erring.
    – Bohemian
    Jan 13, 2017 at 23:38

Noob error is a slangy option in the family of phrases that includes "rookie mistake" and "schoolboy error".

I also suggest howler, which means "a conspicuously stupid error", but which in the context of an expert or professional would convey your intended meaning.

  • The correct slang is newB (as in newbie).
    – user105360
    Jan 15, 2017 at 2:43
  • @Physics-Compute noob and n00b are much more common and widely used than newb.
    – barbecue
    Jan 15, 2017 at 18:38

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