The Collaborative International Dictionary of English v.0.48:

Courser \Cours"er\ (k?rs"?r), n. [F. coursier.]
   1. One who courses or hunts.
      [1913 Webster]

            leash is a leathern thong by which . . . a courser
            leads his greyhound. --Hanmer.
      [1913 Webster]

   2. A swift or spirited horse; a racer or a war horse; a
      charger. [Poetic.] --Pope.
      [1913 Webster]

   3. (Zool.) A grallatorial bird of Europe (Cursorius
      cursor), remarkable for its speed in running. Sometimes,
      in a wider sense, applied to running birds of the Ostrich
      family.
      [1913 Webster]

WordNet (r) 3.0 (2006):

courser
    n 1: a huntsman who hunts small animals with fast dogs that use
         sight rather than scent to follow their prey
    2: formerly a strong swift horse ridden into battle [syn:
       charger, courser]
    3: a dog trained for coursing
    4: swift-footed terrestrial plover-like bird of southern Asia
       and Africa; related to the pratincoles

Moby Thesaurus II by Grady Ward, 1.0:

70 Moby Thesaurus words for "courser":
   Houyhnhnm, Nimrod, antelope, arrow, beater, big game hunter,
   blue darter, blue streak, brood mare, cannonball, charger, colt,
   critter, dart, dobbin, eagle, electricity, entire, entire horse,
   equine, express train, filly, flash, foal, gazelle, gelding,
   greased lightning, greyhound, hare, horse, hunter, huntress,
   huntsman, jacker, jacklighter, jet plane, light, lightning, mare,
   mercury, mount, nag, prancer, quicksilver, rocket, scared rabbit,
   shikari, shot, sportsman, sportswoman, stalker, stallion, steed,
   streak, streak of lightning, striped snake, stud, studhorse,
   swallow, tarpan, thought, thunderbolt, top horse, torrent, trapper,
   trooper, war-horse, white hunter, wild horse, wind