Jailbreak is a Teamplay MOD for Quake 3 Arena. A game of jailbreak consists of two teams, Blue and Red. When killed, you are transported to the enemies jail. While in jail, fellow teammates can free you by hitting the release trigger, or you can work together and use an escape hole located inside of the jail to gain your freedom. Once a team has all opponets in jail they are executed, this being your ultimate goal.
It's a very simple idea and has been used in several other games. It was only a matter of time before it landed in Quake III.