From Longman Dictionary of Contemporary Englishknow what you are talking aboutknow what you are talking aboutspokenKNOW something to know a lot about a particular subject I worked in hotels for years, so I know what I’m talking about. → talk
Examples from the Corpus
know what you are talking about• They have demonstrated publicly, through close scrutiny by their peers, that they know what they are talking about.• Wayne, you don't know what the hell you're talking about.• And those who hint that this approach increases the guilt of the patient simply do not know what they are talking about.• But the debate will be between two insiders who know what they are talking about.• But we ensure we first know what we are talking about.• Engineers should only offer an opinion if they know what they are talking about.• Look, I know what I'm talking about because I was there when it happened.• Rolim seemed to know what he was talking about, but his theories raised some questions for me.• Pilger knows what he is talking about, having spent several years as a reporter in Vietnam.• They are not the only people who know what they are talking about when it comes to children and education. 