Counter-part to the "goalie;" one who will purposely distract unnattractive cockblockers so his/her friend(s) can get laid, even if it means taking home the target cockblock.
Guy 1 - "Dude, that chicks smokin' hot, but her ugly fat friend's a serious cockblock. I need a monster."
Guy 2 - "...you owe me big time for this."
A "Monster" is a Lady Gaga fan, but there is a difference between a "Monster" and "Little Monster". A "Little Monster" is a monster that is 0 - 13 years old and a "Monster" is ages from 14 - 186