The Collaborative International Dictionary of English v.0.48:

Imitate \Im"i*tate\, v. t. [imp. & p. p. Imitated; p. pr. &
   vb. n. Imitating.] [L. imitatus, p. p. of imitari to
   imitate; of unknown origin. Cf. Image.]
   1. To follow as a pattern, model, or example; to copy or
      strive to copy, in acts, manners etc.
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            Despise wealth and imitate a dog.     --Cowlay.
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   2. To produce a semblance or likeness of, in form, character,
      color, qualities, conduct, manners, and the like; to
      counterfeit; to copy.
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            A place picked out by choice of best alive
            The Nature's work by art can imitate. --Spenser.
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            This hand appeared a shining sword to weild,
            And that sustained an imitated shield. --Dryden.
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   3. (Biol.) To resemble (another species of animal, or a
      plant, or inanimate object) in form, color, ornamentation,
      or instinctive habits, so as to derive an advantage
      thereby; sa, when a harmless snake imitates a venomous one
      in color and manner, or when an odorless insect imitates,
      in color, one having secretion offensive to birds.
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WordNet (r) 3.0 (2006):

imitate
    v 1: reproduce someone's behavior or looks; "The mime imitated
         the passers-by"; "Children often copy their parents or
         older siblings" [syn: imitate, copy, simulate]
    2: appear like, as in behavior or appearance; "Life imitate art"
    3: make a reproduction or copy of

Moby Thesaurus II by Grady Ward, 1.0:

98 Moby Thesaurus words for "imitate":
   act like, adopt, affect, ape, appear like, approach, appropriate,
   approximate, assume, be like, be redolent of, bear resemblance,
   borrow, bring to mind, burlesque, call to mind, call up,
   caricature, chorus, come again, come close, come near,
   compare with, copy, correspond, counterfeit, crib, derive from,
   ditto, do, do a repeat, do again, do like, do over, double,
   duplicate, echo, emulate, evoke, fake, favor, follow, forge,
   go like, hoke, hoke up, impersonate, infringe, look like,
   make like, make use of, match, mimic, mirror, mock, monkey, near,
   nearly reproduce, not tell apart, parallel, parody, parrot,
   partake of, pirate, plagiarize, quote, redo, redouble, reduplicate,
   reecho, reflect, regurgitate, reincarnate, remind one of, renew,
   repeat, replicate, reproduce, resemble, revive, satirize, savor of,
   say again, seem like, send up, simulate, smack of, sound like,
   spoof, stack up with, steal, suggest, take, take after, take off,
   take on, take over, travesty