Definify.com
Webster 1913 Edition
Air pump
Air′ pumpˊ
.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.