The Collaborative International Dictionary of English v.0.48:

Horde \Horde\ (h[=o]rd), n. [F. horde (cf. G. horde), fr. Turk.
   ord[=u], ord[imac], camp; of Tartar origin.]
   1. A wandering troop or gang; especially, a clan or tribe of
      a nomadic people migrating from place to place for the
      sake of pasturage, plunder, etc.; a predatory multitude.
      --Thomson.
      [1913 Webster]

   2. Hence: Any large group of people or animals, especially
      one wandering or moving about; as, the movie star was
      surrounded by a horde of screaming fans.
      [PJC]

WordNet (r) 3.0 (2006):

horde
    n 1: a vast multitude [syn: horde, host, legion]
    2: a nomadic community
    3: a moving crowd [syn: drove, horde, swarm]