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]