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