When someone (in a first person shooter game) appears at the last second and steals my kill because he somehow put the last bullet into the noob I've been shooting at.
In Halo 2 - when anyone steals your kill right before you were about to put the final bullet in someone's head or heart. Hence the name: Janitor = Anyone who comes in and cleans up the "crap" they never started.
by RAIN January 27, 2005