A person who calls practically everyone a noob, so noone suspect that he is the only real noob. The meaning of "slut" comes from that nub sluts are usually 10-13 years old and have very soft voices, which make them female-like. The second reason for "slut" is that nub sluts usually use leetspeak, which, when pronounced is similiar to prostitute accent.
Nub Slut: I pownd u u suck ur anoob!!##5
Nub Slut: WTF, how did u kill me ure fuckin nub hacker.