The Collaborative International Dictionary of English v.0.48:

Harpy \Har"py\ (h[aum]r"p[y^]), n.; pl. Harpies (-p[i^]z). [F.
   harpie, L. harpyia, Gr. "a`rpyia, from the root of "arpa`zein
   to snatch, to seize. Cf. Rapacious.]
   1. (Gr. Myth.) A fabulous winged monster, ravenous and
      filthy, having the face of a woman and the body of a
      vulture, with long claws, and the face pale with hunger.
      Some writers mention two, others three.
      [1913 Webster]

            Both table and provisions vanished quite.
            With sound of harpies' wings and talons heard.
                                                  --Milton.
      [1913 Webster]

   2. One who is rapacious or ravenous; an extortioner.
      [1913 Webster]

            The harpies about all pocket the pool. --Goldsmith.
      [1913 Webster]

   3. (Zool.)
      (a) The European moor buzzard or marsh harrier (Circus
          [ae]ruginosus).
      (b) A large and powerful, double-crested, short-winged
          American eagle (Thrasa["e]tus harpyia). It ranges
          from Texas to Brazil.
          [1913 Webster]

   Harpy bat (Zool.)
      (a) An East Indian fruit bat of the genus Harpyia (esp.
          Harpyia cephalotes), having prominent, tubular
          nostrils.
      (b) A small, insectivorous Indian bat (Harpiocephalus
          harpia).

   Harpy fly (Zool.), the house fly.
      [1913 Webster] Harquebus

WordNet (r) 3.0 (2006):

harpy
    n 1: a malicious woman with a fierce temper [syn: vixen,
         harpy, hellcat]
    2: (Greek mythology) vicious winged monster; often depicted as a
       bird with the head of a woman
    3: any of various fruit bats of the genus Nyctimene
       distinguished by nostrils drawn out into diverging tubes
       [syn: harpy, harpy bat, tube-nosed bat, tube-nosed
       fruit bat]
    4: large black-and-white crested eagle of tropical America [syn:
       harpy, harpy eagle, Harpia harpyja]