A female friend that ( with the best intentions ) tries to set up a guy with random girls at a party. Generally by getting too drunk and approaching groups of girls, whispering and pointing at the guy. Thereby destroying any chance he has of getting with the girls.
Cher - Heeeyyyy Dya mind if my friend Mark dances with usss, Heeesh really niice...And heeeeesh shingle (wink)
Phil - Hey Mark, Cher is totally messing shit up for you with those girls. Shes making you look a total mong
Mark - I know dude, She is a proper Cockless Blocker when she's hammered.