The Collaborative International Dictionary of English v.0.48:

Role \Role\, Role \R[^o]le\, n. [F. See Roll.]
   A part, or character, performed by an actor in a drama;
   hence, a part of function taken or assumed by any one; as, he
   has now taken the role of philanthropist.
   [1913 Webster]

   Title role, the part, or character, which gives the title
      to a play, as the part of Hamlet in the play of that name.
      [1913 Webster]

WordNet (r) 3.0 (2006):

role
    n 1: the actions and activities assigned to or required or
         expected of a person or group; "the function of a teacher";
         "the government must do its part"; "play its role" [syn:
         function, office, part, role]
    2: an actor's portrayal of someone in a play; "she played the
       part of Desdemona" [syn: character, role, theatrical
       role, part, persona]
    3: what something is used for; "the function of an auger is to
       bore holes"; "ballet is beautiful but what use is it?" [syn:
       function, purpose, role, use]
    4: normal or customary activity of a person in a particular
       social setting; "what is your role on the team?"