What do you mean

Letting them know you are about to slap the shit out of them so they can take back what they just said

Jack: “I think Games of Thrones Season 8 was actually decent.”
Bill: “Wait what do you mean?”

You know what that means, FISH

This is what you say when you are or become a retard. or it is a dumb joke.

You me, gas station. what are we getting for dinner? sushi of course! uh oh there was a ruffe in our gas station sushi. we blackout and wake up in a sewer, we're surrounded by fish. horny fish. You know what that means, FISH orgy. the stench drives in a bear, what do we do? we're gonna fight it. bear fight, bear handed, bear naked? oh yes please. we befriend the bear after we beat it in a brawl. then we ride it into a chucky cheese. dance, dance revolution. revolution? overthrow the government, uuuh I think so. next thing you know, I'm reincarnated as Jesus Christ, then I turn into a jet, fly into the sun, blackout again, wake up, do a bump, white out which I didn't know you could do. then I smoked a joint, greened out, then I turned into the sun, uh oh looks like the meth is kicking in, uuubgghhhugghhuuaaahhhhaahhhhAAAHHHHHHHH!!!!!