Dictionary.net

one for exhausting or forcing in air.

instrument used in producing a vacuum.

A pump for removing from the condenser of a steam-engine the condensed steam, the water that has produced the condensation, and any air that may have got into the condenser.

An engine for exhausting air from a closed space, or receiver, so as to obtain a more or less perfect vacuum.

n. A machine, variously constructed , for exhausting the air from a closed vessel.