I. |ən+ adjective
Etymology: Middle English, from un- (I) + thinken to think + -able
1. : extraordinary , unimaginable
unthinkable joy
2.
a. : incapable of being thought : not conceivable by the mind
either alternative is unthinkable
b. : contrary to what is reasonable or probable : incredible
it seemed unthinkable that this quiet and apparently worthy citizen should be connected with crimes — F.W.Crofts
3. : not to be considered : being out of the question
the average tenor was unthinkable in these youthful parts — James Joll
• un·think·able·ness noun
• un·thinkably “+ adverb
II. “+ noun
: something unthinkable
the realm of the disharmonic unthinkables — A.E.Wiggam