Doc Rivers says the leaked Donald Trump convo is NOT locker room talk -- as it was described by Donald -- at least not any locker room that he's been in.

TMZ Sports talked to Doc outside Catch restaurant in L.A. Sunday night ... and asked the Clippers coach whether he's heard similar Trump-Bush talk in the locker room.

Doc would know ... he's spent the last 30+ years playing and coaching in the NBA.

FYI -- Trump and Rivers used to be friends ... eating dinner together at a swanky L.A. steakhouse last year.

Clearly those days are long gone. Check out the clip!