The Collaborative International Dictionary of English v.0.48:

Redskin \Red"skin`\ (-sk?n`), n.
   1. A common appellation for a North American Indian; -- so
      called from the color of the skin. It is now considered
      pejorative by some persons of North American Indian
      heritage. --Cooper.
      [1913 Webster +PJC]

   2. (Football) A member of the Washington Redskins, a football
      team.
      [PJC]

WordNet (r) 3.0 (2006):

Redskin
    n 1: (slang) offensive term for Native Americans [syn:
         Redskin, Injun, red man]

The Devil's Dictionary (1881-1906):

RED-SKIN, n.  A North American Indian, whose skin is not red -- at
least not on the outside.