I am looking for a word or phrase regarding something that is "impossible". I can't seem to put my finger on it, but I am trying to think of the word to describe something that is the top of the top, and thus impossible to achieve?

The only two words I have come up with are elusive and formidable, neither of which really mean what I want them to mean. I want something more clever to put it plainly.

  • Why not just enter "impossible synonyms" on Google? It'll give you a whole bunch in first link.
    – Misha R
    Commented Jul 7, 2015 at 23:00
  • 2
    Can you give us a sentence with a blank where the word should be? Commented Jul 7, 2015 at 23:05
  • 1
    "impossible to achieve" unachievable?
    – Avon
    Commented Jul 7, 2015 at 23:08
  • By the way " I can't seem to put my figure on it" is more usually " I can't seem to put my finger on it". Commented Jul 7, 2015 at 23:12
  • It took you a bunch of words to describe this; sometimes that's the way languages work. A great thing about language is two words will often do: utterly unattainable", etc, with the adverb clinching the deal. Commented Jul 7, 2015 at 23:26

4 Answers 4



(when) pigs fly
(when) hell freezes over


Unassailable sounds like it might fit the bill.

  1. Impossible to dispute or disprove; undeniable: unassailable truths.
  2. Not subject to attack or seizure; impregnable: an unassailable fortress.


Example sentence:

Liverpool football club are still looking unassailable.

Which is synonymous with:

Defeating Liverpool football club still looks impossible.



Not able to be reached or achieved:

an unattainable goal


Herculean task

A herculean task is an extremely difficult task; an almost impossible undertaking.

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