What is a word which means something difficult or close to impossible to achieve? For example,

A ten-percent growth rate is a __: it is certainly possible on paper, but very difficult to accomplish.

I can think of a castle in the air or an ideal prospect, but I would love to have a simple one-word substitute.

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    Sorry for being off topic, but wicked problems are problems which are very tough to solve. Mar 26, 2012 at 14:29
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    We're really trying to avoid using this site for "single word requests." If you have a particularly interesting problem to solve, all we ask is that you include a bit of background and context for asking the question, instead of just repeating the title in the question again. See: meta.english.stackexchange.com/questions/1654/… or meta.english.stackexchange.com/questions/2160/… Mar 26, 2012 at 18:47
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    How can we tell people this while maintaining a single-word-requests tag? I mean no dissent. Mar 26, 2012 at 20:33
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    @JeffAtwood: I only have one question for you: how does a poster know beforehand if there is a single perfect answer for his question? I have participated in questions both as an asker and answerer where we ended up zeroing in on one answer. I assumed that this would also be one such question.
    – Bravo
    Mar 27, 2012 at 4:14
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    @JefAtwood: As you may recall, the most-upvoted answers to those Meta questions you posted were for allowing SWRs, provided that they were somewhat interesting and provided some background. This question arguably does that, so perhaps it would have been better if people had been able to vote to close (or not). For the recond, I personally dislike SWRs, but some people do like the more complicated ones, like this one. Mar 27, 2012 at 8:41

20 Answers 20


A pipe dream may be what you're looking for; possible, but impossible for all practical purposes.

A plan, desire, or idea that will not likely work; a near impossibility.

"I think that his plan to become a professional athlete is a pipe dream and that he should stay in school."

  • The brass ring ...
    – GEdgar
    Mar 26, 2012 at 14:06

A ten-percent growth rate is unrealistic: it is certainly possible on paper, but very difficult to accomplish.

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    The OP seems to be looking for a noun.
    – Robusto
    Mar 26, 2012 at 14:39

I know this isn't one word, but will suggest Herculean task

A ten-percent growth rate is a Herculean task: it is certainly possible on paper, but very difficult to accomplish.

  • But I think "Herculean task" implies that it is, in fact, possible, just very difficult, which is rather different from "not really possible in practice".
    – Jay
    Mar 29, 2012 at 21:34
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    I think it fits better than that, meaning more than difficult, near impossible for humans. It implies it's mythologically possible, a task fit for the gods and progeny not mere mortals, not practically realistically achievable except in stories.
    – Tyeth
    Feb 5, 2021 at 13:51


A ten-percent growth rate is an impracticality: it is certainly possible on paper, but very difficult to accomplish.

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    +1 This keeps consistent with the second part, where unrealistic implies directly that it is not even possible.
    – user14070
    Mar 26, 2012 at 14:41

I can't believe nobody mentioned it so far:


a thing which is hoped for but is illusory or impossible to achieve:

the economic sovereignty you claim to defend is a chimera

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    I think that definition is to all intents and purposes "incorrect". I don't doubt chimera is occasionally used with the sense of illusory, but I think this is primarily by people who don't actually know what the word really means. Mar 26, 2012 at 14:53
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    @FumbleFingers: that would include the OED, then. "An unreal creature of the imagination, a mere wild fancy; an unfounded conception. (The ordinary modern use.)" Mar 26, 2012 at 15:11
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    @TimLymington: I don't think I'm exactly disagreeing with OED, but I just don't think, for example, unrealistic sales targets can be properly called a chimera. To me, the word primarily means an unreal creature of mixed parentage, which can metaphorically extend to an untenable conceptualisation deriving from mutually incompatible antecedents. I don't see it extending to overoptimistic ambitions in general. Mar 26, 2012 at 15:39
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    I upvoted because I've never heard that definition before, but I would tend to disagree with OED on this one. Perhaps there are a bunch of literary references that I'm unfamiliar with, but I've never seen it used like in their example sentence. I've always seen it used to refer to something that is created through combination (and not always unreal, although always freakish.)
    – jhocking
    Mar 26, 2012 at 18:01
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    I'm familiar with this metaphor in my own language and I believe I've heard it used in English as well on several occasions. I honestly didn't think it would be unknown to so many people. Mar 26, 2012 at 18:34

I have heard business managers call such a situation a challenge. When everyone in the room knows that the financial goal the managers just set forth is going to take a Herculean effort to achieve, they often follow up by saying something like, "We know this will be a challenge, but...."

In this case, it would used in the sense of this definition:

  1. A test of one's abilities or resources in a demanding but stimulating undertaking.

Impossible, unrealistic, unattainable, unachievable, quixotic, dreamy, empty, even as a non-native English speaker, I can think up many analogues. Just for your fun, we call unrealistic story / plan “a story like a dream,’ 'a cake drawn in the picture (that you can not eat) - 画餅', and ‘castle in the air –空中楼閣', or 'castle on the sand -砂上の楼閣' as well in Japanese.


unattainable might be the word you're looking for.

unattainable (adjective) Pronunciation: /ʌnəˈteɪnəb(ə)l/ not able to be reached or achieved: an unattainable goal

You would end up with a phrase like this:

A ten-percent growth rate is unattainable: it is certainly possible on paper, but very difficult to accomplish.

I hope it helps.

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    If it's possible on paper, it isn't unattainable, merely very difficult. Mar 26, 2012 at 13:19
  • You set the goal or growth rate on paper, but it is not possible to achieve such goal/target in the real world. Otherwise the action of writing something unattainable would convert such action into something feasible. Mar 26, 2012 at 13:41
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    Something that can be attained (however difficult) is not unattainable. Using the word in OPs context is akin to the common misuse of literally. Mar 26, 2012 at 14:06

I'd go with unfeasible. For example:

A ten-percent growth rate is unfeasible: it is certainly possible on paper, but very difficult to accomplish.

Inverting the dictionary.com definition for feasible, you get:

un·fea·si·ble adjective

  1. not capable of being done, effected, or accomplished: an unfeasible plan.
  2. improbable; unlikely: an unfeasible theory.
  3. unsuitable: a road unfeasible for travel.

Of course, the noun version is not quite countable. You could talk about the "unfeasibility of" something and that's fine, but to describe something as "an unfeasibility" sounds particularly awkard to me.


For that scenario I think aspiration is a good choice.

A ten-percent growth rate is an aspiration

Aspirations are typically things that people or organisations want to achieve, think they can, but cannot guarantee that they will. In business it's typically the best case scenario or outcome of a particular course of action.

A similar word is ambition.

In a more fanciful context, I would use dream.

There's no way I'll make it to the top of Everest with my asthma, it's just a dream.

  • Thank you, "aspirational" was a word I was looking for today, as in "I signed up for the theater schedules reminders - it was more aspirational than anything else."
    – Michael H.
    Apr 25, 2018 at 21:40


A ten-percent growth rate is an improbability: it is certainly possible on paper, but very difficult to accomplish.

Hope this is right.


Though not a noun, sisyphean is one of my more favorite words. It means:

Endless and unavailing, as labor or a task

From the son of Aeolus and ruler of Corinth, noted for his trickery: he was punished in Tartarus by being compelled to roll a stone to the top of a slope, the stone always escaping him near the top and rolling down again.


To toss out a couple: daunting? formidable?


a Stretch Goal, or a Big Hairy Audacious Goal(BHAG) would be the terms I would use in formal and informal contexts, respectively.


What about the word "Utopia"? In Y. C. Zarka's 28 Aug 2011 NYT blog one finds

Utopia is often spoken of in a general, imprecise way, to characterize any conception of the state that is considered an unrealizable ideal.

  • Utopia as such does not fill in there. Perhaps an utopian prospect or something does.
    – Bravo
    Mar 26, 2012 at 14:24

I'd suggest, pie in the sky

something good that is ​unlikely to ​happen: I ​wanted to be a ​major ​league ​baseball ​player, but I ​knew it was ​probably pie in the ​sky.

Cambridge Dictionaries Online

A ten-percent growth rate is just pie in the sky: it is certainly possible on paper, but very difficult to accomplish.


Not a single word, but here is an idiom which I casually came across that might interest future visitors. It means to attempt the impossible, or to place one difficulty on top of another.

To pile (or heap) Pelion on Ossa

a. to make matters worse; aggravate or compound a situation.
b. to engage in vain or futile efforts.
Random House Kernerman Webster's College Dictionary

Otus and Ephialtes were the ambitious twin sons of Poseidon. In their greed and quest to conquer Olympus they threatened to pile two mountains on top of each other. Mount Olympus is said to have been the bottom mountain, with Mounts Ossa and Pelion upon Ossa as second and third.

The rather sophisticated idiom in the OP's sentence would look like this

A ten-percent growth rate is like piling Pelion on Ossa:

In Greek mythology, Mount Pelion was the place where Achilles' parents, Thetis and Peleus were married. The goddess Eris, who was not invited, brought a golden apple to the wedding party with the inscription "To the Fairest". The dispute which ensued between the goddesses Hera, Aphrodite and Athena led to the Trojan War. Greek Gods and Goddesses


The first thing that came to mind for me was "an insurmountable task."


If it something could be possible, but is difficult/unlikely, you might consider the more informal stretch or reach, as in

A five-percent growth is certainly doable; a ten-percent growth is a reach.


Elusive: Difficult to find, catch, or achieve; Difficult to remember or recall.

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