Video game lingo often used when playing a first-person-shooter online, meaning to run around the map whilst making many kills by repeating the same tactic(s); the opposite of being a camper
Greg: Alright, so I was playing Modern Warfare 2, and I tried camping at Crash.
Greg: This guy kept running around the map tac knifing everybody. He even called in a nuke!
Fred: What a freakin' hiker!