The Collaborative International Dictionary of English v.0.48:

Impersonate \Im*per"son*ate\, v. t. [imp. & p. p.
   Impersonated; p. pr. & vb. n. Impersonating.]
   1. To invest with personality; to endow with the form of a
      living being.
      [1913 Webster]

   2. To ascribe the qualities of a person to; to personify.
      [1913 Webster]

   3. To assume, or to represent, the person or character of; to
      personate; as, he impersonated Macbeth.
      [1913 Webster]

            Benedict impersonated his age.        --Milman.
      Impersonation

WordNet (r) 3.0 (2006):

impersonate
    v 1: assume or act the character of; "She impersonates Madonna";
         "The actor portrays an elderly, lonely man" [syn:
         impersonate, portray]
    2: represent another person with comic intentions
    3: pretend to be someone you are not; sometimes with fraudulent
       intentions; "She posed as the Czar's daughter" [syn: pose,
       impersonate, personate]

Moby Thesaurus II by Grady Ward, 1.0:

57 Moby Thesaurus words for "impersonate":
   act, act a part, act as, act out, adumbrate, ape, body forth, copy,
   copycat, create a role, demonstrate, depict, discourse, do, embody,
   enact, exemplify, figure, foreshadow, hit off, hit off on,
   illustrate, image, incarnate, make false pretenses, masquerade as,
   mime, mimic, mirror, mock, pantomime, parrot, pass for, perform,
   personate, personify, play, play a part, play a role,
   play opposite, playact, portray, pose as, prefigure, pretend to be,
   pretypify, project, realize, reflect, represent, shadow,
   shadow forth, support, sustain a part, take a part, take off,
   take off on