The Collaborative International Dictionary of English v.0.48:

Impersonation \Im*per`son*a"tion\, Impersonification
\Im`per*son`i*fi*ca"tion\, n.
   The act of impersonating; personification; investment with
   personality; representation in a personal form.
   [1913 Webster]

WordNet (r) 3.0 (2006):

impersonation
    n 1: a representation of a person that is exaggerated for comic
         effect [syn: caricature, imitation, impersonation]
    2: pretending to be another person [syn: imposture,
       impersonation]
    3: imitating the mannerisms of another person [syn:
       impersonation, personation]

Moby Thesaurus II by Grady Ward, 1.0:

59 Moby Thesaurus words for "impersonation":
   acting, aping, buffoonery, business, characterization, copying,
   counterfeiting, dumb show, embodiment, emulation, enacting,
   enactment, fakery, following, forgery, gag, ham, hammy acting,
   hit-off, hoke, hokum, imitation, imposture, impression,
   incarnation, masquerade, mimesis, mimicking, mimicry, miming,
   mirroring, mummery, onomatopoeia, overacting, pantomime,
   pantomiming, parody, patter, performance, performing, personation,
   personification, plagiarism, plagiary, playacting, playing,
   portrayal, posing, projection, repetition, representation,
   simulation, slapstick, stage business, stage directions,
   stage presence, stunt, takeoff, taking a role