What is "escape valve"

Escape \Es*cape"\, n.

1. The act of fleeing from danger, of evading harm, or of avoiding notice; deliverance from injury or any evil; flight; as, an escape in battle; a narrow escape; also, the means of escape; as, a fire escape.

   I would hasten my escape from the windy storm.
   --Ps. lv. 8.

2. That which escapes attention or restraint; a mistake; an oversight; also, transgression. [Obs.]

   I should have been more accurate, and corrected all those former escapes.
   --Burton.

3. A sally. ``Thousand escapes of wit.''
   --Shak.

4. (Law) The unlawful permission, by a jailer or other custodian, of a prisoner's departure from custody.

5. (Bot.) A plant which has escaped from cultivation.

   Note: Escape is technically distinguishable from prison breach, which is the unlawful departure of the prisoner from custody, escape being the permission of the departure by the custodian, either by connivance or negligence. The term escape, however, is applied by some of the old authorities to a departure from custody by stratagem, or without force.
   --Wharton.

   5. (Arch.) An apophyge.

6. Leakage or outflow, as of steam or a liquid.

7. (Elec.) Leakage or loss of currents from the conducting wires, caused by defective insulation.

   Escape pipe (Steam Boilers), a pipe for carrying away steam that escapes through a safety valve.

   Escape valve (Steam Engine), a relief valve; a safety valve. See under Relief, and Safety.

   Escape wheel (Horol.), the wheel of an escapement.

n. a valve in a container in which pressure can build up (as a steam boiler); it opens automatically when the pressure reaches a dangerous level [syn: safety valve, relief valve, escape cock, escape]