What do people mean when they say "check your privilege" to someone they know nothing about? Is this implied to mean white guilt? Or wealth?

That's how people with white guilt shut down people who don't. It's how nonwhites mock and attempt to silence whites. It's also used as a joke in irreverent circles.

It's a liberal tagline that explains that whites have it easier than other races. It's somewhat true, as American culture IS a conglomerate of European cultures. Of course, America pushes the idea of the term "white" which is a purely American.

Hispanics do fair better than blacks in America as blacks have redefined American culture as white culture which the majority want to not join. Instead, they have created their own subculture separate of American culture which All but guarantees their ostracized position. (As a caveat, I will agree that for a very long time, American culture pushed by the "white" segregationists didn't accept blacks, but once the new generation began to accept, blacks began to create their own subculture and set back a larger conglomerate American Culture.)

They mean "I don't want to listen to your opinions because you're white".

Seriously it's just a slogan of a cult. It means about as much to me as a Scientologist saying I need to check my thetans or something. I just laugh and walk away.

Trump didn't check his