The Collaborative International Dictionary of English v.0.48:

Force pump \Force" pump`\ (Mach.)
      (a) 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.
      (b) 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.
          [1913 Webster]

WordNet (r) 3.0 (2006):

force pump
    n 1: pump used to force a liquid up and expel it under pressure