vacuum pump

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A pump used to evacuate an enclosure.

from The Century Dictionary.

• noun A pump consisting of a chamber or barrel, a suctionpipe with a valve to prevent return flow, a discharge-pipe which has a valve that is closed when the chamber is emptied, and a steam induction-pipe provided with a valvethat is opened when the chamber is filled with water, and closed when the chamber is filled with steam.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A piece of equipment used for extraction of gas or vapour from an enclosed space, leaving the container with a partial vacuum.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a pump that moves air in or out of something