Something yelled at times of stress.
Origin: First heard echoing from the Video Game room in Hendrix, across the hall from the Forum (circa 1984). Often when the sound of the player in Centipede being killed was heard, there would be a loud call of "BUMBACLAA!" in a Jamacian accent.Background from http://www.urbandictionary.com/define.php?term=bumbaclot:
Bumbaclot, the acme of Jamaican swearing, translates literally as "arsewipe". Its real meaning is more like a slow, surprised "motherfucker"