First discovered and used on a closed meeting between backpackers ('backpacker' can also mean the same thing) in Chiang Mai, Thailand, January 2009.
The definition is simple; Someone (or something) that blocks your bodys' exit.
Dude 2: No, I had a life, why?
Dude 1: Gyllenhaals butt got pretty owned by Heath Ledger!
Dude 2: Oh man! What a friggin' exit blocker!