A big penis.
Man: Honey, I have a thick stick.
Woman: No you don't.
Man: ...No I don't.
Originated in California, "what's thick?" is basically another term for a "booty call". Asking what's thick? To a person that isn't really "thick" is basically an offense.
Hey Jasmine, damn you look fine. So what's thick?
A girl who’s has a lot of meat on her body but isn’t too fat!
Fat, lots of meat, chubby, chunky around the edges
Have you ever seen fat Amy, she is so thick
British slang for stupid (thick skull)
Brits: He seems nice but he’s very thick
Americans:😳