know what (one) is talking about

know what (one) is talking about

To be adequately knowledgeable about or experienced in something one is discussing. Mister, I don't think you know what you're talking about. There's no way these old pipes can withstand that kind of pressure!

See also: know, talk, what

Farlex Dictionary of Idioms. © 2024 Farlex, Inc, all rights reserved.

know what you’re ˈtalking about

(informal) have good knowledge of something; be an expert on something: I really enjoyed that lecture. She certainly knows what she’s talking about. ♢ That history teacher doesn’t know what he’s talking about. He makes a lot of mistakes.

See also: know, talk, what

Farlex Partner Idioms Dictionary © Farlex 2017