Airtight chamber that allows people to pass between areas of different pressure; also an air bubble in a pipe that impedes fluid flow. An air lock may connect an environment at ordinary pressure and an environment that has high air pressure (such as a submerged caisson used for tunneling or building dams or bridge foundations).
An air lock may also permit someone wearing breathing apparatus to pass into an airless environment (into water from a submerged submarine or into the vacuum of space from a spacecraft).
A chamber that provides access to space where air is under pressure; SYN. airlock. air-lock

(Homonym: loch).
1. A fastener fitted to a door or drawer to keep it firmly closed.
2. A device incorporated into the ignition switch to prevent the use of a vehicle by persons who do not have the key; SYN. ignition lock.
3. A mechanism that detonates the charge of a gun.
4. A strand or cluster of hair; SYN. curl, ringlet, whorl.
5. Any wrestling hold in which some part of the opponent's body is twisted or pressured.
6. Section of canal that can be closed to control the water level; used to raise or lower vessels that pass through it; SYN. lock chamber.
Construction installed in waterways to allow boats or ships to travel from one level to another. The earliest form, the flash lock, was first seen in the East in 1st-century-AD China and in the West in 11th-century Holland. By this method barriers temporarily dammed a river and when removed allowed the flash flood to propel the waiting boat through any obstacle. This was followed in 12th-century China and 14th-century Holland by the pound lock. In this system the lock has gates at each end. Boats enter through one gate when the levels are the same both outside and inside. Water is then allowed in (or out of) the lock until the level rises (or falls) to the new level outside the other gate.
Locks are important to shipping where canals link oceans of differing levels, such as the Panama Canal, or where falls or rapids are replaced by these adjustable water “steps”.

ETYM Old Fren. escluse, French écluse, Late Lat. exclusa, sclusa, from Latin excludere, exclusum, to shut out: cf. Dutch sluis sluice, from the Old French. Related to Exclude.
Carries a rapid flow of water controlled by a sluicegate; SYN. sluiceway, penstock.

A gate in a sluice that can control the flow of water; SYN. floodgate.

1. A gate for shutting out, admitting, or releasing a body of water; sluice
2. Something serving to restrain an outburst