The Collaborative International Dictionary of English v.0.48:

Redcoat \Red"coat`\ (-k[=o]t`), n.
   One who wears a red coat; specifically, a red-coated British
   soldier.
   [1913 Webster]

WordNet (r) 3.0 (2006):

redcoat
    n 1: British soldier; so-called because of his red coat
         (especially during the American Revolution) [syn:
         redcoat, lobsterback]

Moby Thesaurus II by Grady Ward, 1.0:

20 Moby Thesaurus words for "redcoat":
   Anzac, Aussie, Boche, Fritz, GI, Heinie, Hun, Jerry, Johnny, Kraut,
   Tommy, Tommy Atkins, Yank, askari, digger, doughboy, jock, poilu,
   sepoy, swaddy