'Escape valve' definitions:

Definition of 'escape valve'

noun

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 valve, escape cock, escape]

Definition of 'Escape valve'

From: GCIDE

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. [1913 Webster]
I would hasten my escape from the windy storm. --Ps. lv. 8. [1913 Webster]
2. That which escapes attention or restraint; a mistake; an oversight; also, transgression. [Obs.] [1913 Webster]
I should have been more accurate, and corrected all those former escapes. --Burton. [1913 Webster]
3. A sally. "Thousand escapes of wit." --Shak. [1913 Webster]
4. (Law) The unlawful permission, by a jailer or other custodian, of a prisoner's departure from custody. [1913 Webster]
5. (Bot.) A plant which has escaped from cultivation. [Webster 1913 Suppl.]
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. [1913 Webster]
5. (Arch.) An apophyge. [1913 Webster]
6. Leakage or outflow, as of steam or a liquid. [1913 Webster]
7. (Elec.) Leakage or loss of currents from the conducting wires, caused by defective insulation. [1913 Webster]
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. [1913 Webster]