What does that mean? I read it somewhere in relation to friend-zoned..
I've never heard it before, but if it's related to being friend-zoned, it's presumably a neologism based on jemandem einen Korb geben, which literally means "to give someone a basket" but idiomatically means "to refuse someone's advances, to turn someone down, to rebuff someone".
So if you wanted to hook up with a girl but she "gave you a basket", she said no.
Some people might call that "being friend-zoned", though perhaps a better explanation might be that the woman does not owe it to you to be anything more than a friend.
I have never heard "gekorbt" but there is an expression "einen Korb bekommen"/ "jmd. einen Korb geben" which is colloquial for "to rebuff / to turn someone down". Maybe in some areas they made a verb out of it? In any case it would be extremly colloquial.