A phrase used in response to a question or command in which the target person does not know the answer to or how to respond.

(informal) Expresses dismay or annoyance, especially at misfortune.

A request for information.

Polite request

(transitive, idiomatic) To know (something or someone) very thoroughly.

(of the giving of information) remaining secret or hidden until it is needed to be known (by a particular party).

(usually in the past tense) To have known a famous person before he or she was famous.

(idiomatic) A phrase used to get someone's attention before announcing something.

The name of something the speaker does not want to mention, but which is known, or very likely to be known, to the listener. It can be plural (as in "... the you-know-whats").

(chiefly US, in negative constructions) To know something, even if only a little, about. / (chiefly US, idiomatic) To know nothing, or almost nothing, about.