Any psychological mechanism to relieve stress.
A valve on a boiler to let the steam escape.
Any mechanism offering relief from pressure or tension, e.g. emotionally.
A relief valve set to open at a pressure below that at which a container (such as a boiler) would burst.
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.