Male or female that is notorious for dating friend's exes or people that friends have previously dated. Usually this person attacks almost immediately after a break-up to waste no time and doesn't care what anyone thinks about his/her actions.
Friend 1: Mike and Laney just broke up... and Mike's friend Joe is already messaging her on Facebook, WTF
Friend 1: Dude, Joe did the same thing with the last chick I hooked up with. He's got no shame, total ex-chaser.