Noun
A pump having a solid piston, or plunger, for drawing and forcing a liquid, as water, through the valves; in distinction from a pump having a bucket, or valved piston.
A pump adapted for delivering water at a considerable height above the pump, or under a considerable pressure; in distinction from one which lifts the water only to the top of the pump or delivers it through a spout. See Illust. of Plunger pump, under Plunger.
Source: Webster's dictionaryforce-pump