For internal combustion engines, the pipe that vents waste gases from the engine.
On a steam locomotive, a pipe which takes away steam exhausted from a cylinder.
A relief valve set to open at a pressure below that at which a container (such as a boiler) would burst.
Any mechanism offering relief from pressure or tension, e.g. emotionally.
A United States law, codified at 18 USC §3553(f), authorizing a judge to disregard mandatory minimum sentences for some criminals with few or no prior offenses.