you know what phrase 1you-know-what pronoun 1 phrase1 •Used, often as a question, to get someone's attention before announcing something.Well, you know what, he's got a cloud over him. You have to live with who you are and make your peace with your maker about what you really are. — 2001 you-know-what pronoun1 •The name of something the speaker does not want to mention, but which is known, or very likely to be known, to the listener.
