kate: your a wanker
alex: u just called me a wanker so ur the wanker
person 1: Did you see that wanker over there?
person 2: yeah i heard he was really annoying
jeff:hey, i got you lunch!
you: thanks jeff! you're such a wanker!
1 - Someone who wanks.
2 - An insult.
Bonus note: wanking is male masturbation
"Piss off, you wanker!"