air pump

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A pump for compressing, removing, or forcing a flow of air.

Century Dictionary and Cyclopedia

1. n. An apparatus for the exhaustion, compression, or transmission of air. Air-pumps are used for many purposes, and are made in a variety of forms, which differ according to the uses that they serve. In the more common forms the air is exhausted by means of a cylinder and piston, as in Ritchie's air-pump (see cut), or by centrifugal action. Rotating buckets dipping into water, which forms a seal, are used for some special purposes; as is also, for slight changes of pressure, a form consisting of a vessel closed at the top and sides but open at the bottom, and dipping to a certain extent into water or other fluid, which forms a seal and prevents the escape of the air. For the Sprengel air-pump, see mercury air-pump, under mercury. The air-pump of a condensing steam-engine is used to maintain a vacuum within the condenser by withdrawing from it air and uncondensed vapor. See air-compressor, aspirator, ejector, pump, steam-jet.

Wiktionary

1. n. A pump that moves air either into, or out of, something.

GNU Webster's 1913

1. (Physics) A kind of pump for exhausting air from a vessel or closed space; also, a pump to condense air or force it into a closed space.
2. (Steam Engines) A pump used to exhaust from a condenser the condensed steam, the water used for condensing, and any commingled air.

WordNet 3.0

1. n. a pump that moves air in or out of something