Old school term for a chump who is easy to scam or assault verbally and/or physically; normally used to remind an adversary that they, well, suck. Suckas are known to start some mess they cain't finish and can be seen throwing rocks from their glass houses.
Man, you you betta clear on out before I turn my dogs out on you, sucka.
A sucka is the lowest of the lower. Even people who murder babies have the right to declare someone a sucka, if said person fits said description. A sucka is worse than the mentally handicapped monkey who rolls around in his shit. A man who lets his dog crap on someones lawn and doesnt pick up the crap is a douche, but not a sucka.