you–know–what noun
[noncount] informal 1 — used in speech to refer to something that is not named but is known to both the hearer and speaker ▪ I've hidden the you-know-what in the closet. 2 — used in place of a rude or offensive word in order to express anger or annoyance ▪ He's a complete you-know-what. ▪ That's a big pile of you-know-what.
