copycat

from WordNet (r) 3.0 (2006)

copycat
    n 1: someone who copies the words or behavior of another [syn:
         {copycat}, {imitator}, {emulator}, {ape}, {aper}]

from The Collaborative International Dictionary of English v.0.48

copycat \cop"y*cat`\, copy cat \cop"y cat`\n.
   someone who copies the words or behavior of another.

   Syn: imitator, ape, aper.
        [WordNet 1.5]

from Moby Thesaurus II by Grady Ward, 1.0

33 Moby Thesaurus words for "copycat":
      ape, conformist, copier, copyist, counterfeiter, cuckoo,
      dissembler, dissimulator, echo, echoer, echoist, faker, forger,
      hypocrite, imitator, impersonator, impostor, mime, mimer, mimic,
      mimicker, mocker, mockingbird, monkey, parrot, phony, plagiarist,
      poll-parrot, polly, polly-parrot, poseur, sheep, simulator

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