Source : Webster's Revised Unabridged Dictionary (1913)

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}.

Source : WordNet®

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