The Collaborative International Dictionary of English v.0.48:

Rooster \Roost"er\, n.
   The male of the domestic fowl; a cock. [U.S.]
   [1913 Webster]

         Nor, when they [the Skinners and Cow Boys] wrung the
         neck of a rooster, did they trouble their heads whether
         he crowed for Congress or King George.   --W. Irving.
   [1913 Webster]

WordNet (r) 3.0 (2006):

rooster
    n 1: adult male chicken [syn: cock, rooster]

Moby Thesaurus II by Grady Ward, 1.0:

72 Moby Thesaurus words for "rooster":
   Bantam, banty, barn-door fowl, barnyard fowl, biddy, billy,
   billy goat, boar, broiler, brooder, broody hen, bubbly-jock, buck,
   bull, bullock, capon, chanticleer, chick, chickabiddy, chicken,
   chicky, cock, cockerel, dog, domestic fowl, drake, duck, duckling,
   dunghill fowl, entire, entire horse, fowl, fryer, game fowl,
   gander, gobbler, goose, gosling, guinea cock, guinea fowl,
   guinea hen, hart, he-goat, hen, hen turkey, partlet, peacock,
   poulard, poult, poultry, pullet, ram, roaster, setting hen,
   spring chicken, stag, stallion, steer, stewing chicken, stot, stud,
   studhorse, tom, tom turkey, tomcat, top cow, top horse, tup,
   turkey, turkey gobbler, turkey-cock, wether