Refers to a Halo 2 game on Xbox Live, where a player (usually in MatchMaking, but also in Custom games also) enters a game and is simply owning. It is quite easy to kill the noobopponents, almost as easily as a Grunt in Campaign mode, hence the name Grunt Hunt.
Xbox live player: Wow, you guys suck, this is a huge Grunt Hunt, it's pathetic.
