The Union Aerospace Corporation (UAC) is a fictional military-industrial conglomerate from the Doom series of video games created by Id Software . Their focus is primarily military weaponry, weapons and defense contracts, aerospace, bio-research, space exploration, and other more sinister scientific endeavors. It is probably named after the infamous Union Banking Corporation, and may have been inspired by the Weyland-Yutani corporation from the Alien films.

United Aerospace Corporation, the evil corporation in all the Doom games

underground art criminals, they do kick ass grafitti.

Ultimate Adventist Child: Someone who was raised by Seventh-Day Adventists, are really sheltered, and don't know much about worldly things (or things outside of the Bible).

Unauthorized Ass Contact. Occurs when two people try to slide past each other in a narrow space and physical contact accidentally occurs below the belt. Normally this is a non-issue between strangers in a crowded place, but calling out the UAC among co-workers lets the other person know it was an accident and that you're not trying to be gay. Originally coined for use by missile combat crewmembers in Minuteman III launch control centers.

User Account Control: a security system in Microsoft's Windows Vista operating system