Noun

Something that is impossible.

Meeting the deadline is an impossibility ; there is no way we can be ready in time.

(uncountable) The quality of being impossible.

* South

They confound difficulty with impossibility .

{{quote-Fanny Hill, part=2 , ...he threw himself upon her, and his back being now towards me, I could only take his being ingulph'd for granted, by the directions he mov'd in, and the impossibility of missing so staring a mark...}}

(obsolete) Inability; helplessness.

(Latimer)