The Collaborative International Dictionary of English v.0.48:

Counterfeit \Coun"ter*feit\ (koun"t?r-f?t), a. [F. contrefait,
   p. p. of contrefaire to counterfeit; contre (L. contra) +
   faire to make, fr. L. facere. See Counter, adv., and
   Fact.]
   [1913 Webster]
   1. Representing by imitation or likeness; having a
      resemblance to something else; portrayed.
      [1913 Webster]

            Look here upon this picture, and on this
            The counterfeit presentment of two brothers. --Shak.
      [1913 Webster]

   2. Fabricated in imitation of something else, with a view to
      defraud by passing the false copy for genuine or original;
      as, counterfeit antiques; counterfeit coin. "No
      counterfeit gem." --Robinson (More's Utopia).
      [1913 Webster]

   3. Assuming the appearance of something; false; spurious;
      deceitful; hypocritical; as, a counterfeit philanthropist.
      "An arrant counterfeit rascal." --Shak.

   Syn: Forged; fictitious; spurious; false.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Counterfeit \Coun"ter*feit\, n.
   1. That which resembles or is like another thing; a likeness;
      a portrait; a counterpart.
      [1913 Webster]

            Thou drawest a counterfeit
            Best in all Athens.                   --Shak.
      [1913 Webster]

            Even Nature's self envied the same,
            And grudged to see the counterfeit should shame
            The thing itself.                     --Spenser.
      [1913 Webster]

   2. That which is made in imitation of something, with a view
      to deceive by passing the false for the true; as, the bank
      note was a counterfeit.
      [1913 Webster]

            Never call a true piece of gold a counterfeit.
                                                  --Shak.
      [1913 Webster]

            Some of these counterfeits are fabricated with such
            exquisite taste and skill, that it is the
            achievement of criticism to distinguish them from
            originals.                            --Macaulay.
      [1913 Webster]

   3. One who pretends to be what he is not; one who personates
      another; an impostor; a cheat.
      [1913 Webster]

            I fear thou art another counterfeit;
            And yet, in faith, thou bear'st thee like a king.
                                                  --Shak.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Counterfeit \Coun"ter*feit\, v. t. [imp. & p. p.
   Counterfeited; p. pr. & vb. n. Counterfeiting.]
   1. To imitate, or put on a semblance of; to mimic; as, to
      counterfeit the voice of another person.
      [1913 Webster]

            Full well they laughed with counterfeited glee
            At all his jokes, for many a joke had he.
                                                  --Goldsmith.
      [1913 Webster]

   2. To imitate with a view to deceiving, by passing the copy
      for that which is original or genuine; to forge; as, to
      counterfeit the signature of another, coins, notes, etc.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Counterfeit \Coun"ter*feit\, v. i.
   1. To carry on a deception; to dissemble; to feign; to
      pretend.
      [1913 Webster]

            The knave counterfeits well; a good knave. --Shak.
      [1913 Webster]

   2. To make counterfeits.
      [1913 Webster]

WordNet (r) 3.0 (2006):

counterfeit
    adj 1: not genuine; imitating something superior; "counterfeit
           emotion"; "counterfeit money"; "counterfeit works of
           art"; "a counterfeit prince" [syn: counterfeit,
           imitative] [ant: echt, genuine]
    n 1: a copy that is represented as the original [syn:
         counterfeit, forgery]
    v 1: make a copy of with the intent to deceive; "he faked the
         signature"; "they counterfeited dollar bills"; "She forged
         a Green Card" [syn: forge, fake, counterfeit]

Moby Thesaurus II by Grady Ward, 1.0:

296 Moby Thesaurus words for "counterfeit":
   act, act a part, act like, affect, affected, agent, alike,
   alternate, alternative, analogy, ape, aped, apocryphal,
   appear like, approach, approximate, artificial, assume, assumed,
   backup, bad check, bad money, base coin, bastard, be like,
   be redolent of, bear resemblance, bluff, bogus, bogus money,
   borrow, bring to mind, brummagem, call to mind, call up,
   certified copy, change, changeling, cheat, chorus, clinquant, coin,
   colorable, colored, come close, come near, compare with,
   comparison, concoct, consimilar, cook up, copied, copy, correspond,
   counterfeit money, counterfeited, cover up, crib, deceit,
   deception, deceptive, delusive, delusory, deputy, dissemble,
   dissimulate, distorted, ditto, do, do a bit, do like, double,
   dramatize, dressed up, dummy, echo, ectype, embellished,
   embroidered, equal, equivalent, ersatz, evoke, exchange, fabricate,
   facsimile, factitious, fair copy, faithful copy, fake, faked,
   fakement, false, false money, falsified, falsify, fantasize, favor,
   favoring, feign, feigned, fictitious, fictive, fill-in, follow,
   following, forge, forged, forgery, four-flush, frame-up, fraud,
   fraudulent, fudge, gammon, garbled, ghost, ghostwriter, go like,
   green goods, gyp, hatch, histrionize, hoax, hoke, hoke up, hokey,
   homogeneous, humbug, icon, identical, illegitimate, image, imitate,
   imitated, imitation, impostor, insincere, invent, junk, junky,
   kite, let on, let on like, like, likeness, locum tenens, look like,
   make a pretense, make as if, make believe, make like,
   make out like, make up, make-believe, makeshift, man-made,
   manufacture, match, meretricious, metaphor, metonymy, mimic,
   mimicked, mint, mirror, misleading, mock, near, nearly reproduce,
   nearly reproduced, next best thing, not tell apart, not unlike,
   overact, parallel, partake of, paste, pasticcio, pastiche,
   personnel, perverted, phony, picture, pinch, pinch hitter,
   pinchbeck, plagiarize, plagiarized, play, play a part,
   play a scene, play possum, playact, portrait, pretend, pretended,
   profess, provisional, proxy, pseudo, put on, put on airs, put-on,
   put-up job, quasi, queer, reecho, reflect, relief, remind one of,
   repeat, replacement, representation, representative, reproduce,
   reproduction, resemblance, resemble, resembling, reserve, reserves,
   ringer, rip-off, rubber check, savor of, second string, secondary,
   seem like, self-styled, sell, semblance, sham, shoddy,
   shove the queer, sign, similar, similitude, simulacrum, simulate,
   simulated, smack of, smacking of, snide, so-called, soi-disant,
   something like, sound like, spare, spares, spurious, stack up with,
   stand-in, stopgap, sub, substituent, substitute, substitution,
   succedaneum, suggest, suggestive of, superseder, supplanter,
   supposititious, surrogate, swindle, symbol, synecdoche, synthetic,
   take after, temporary, tentative, third string, tin, tinsel,
   titivated, token, trump up, tug the heartstrings, twisted,
   unauthentic, understudy, ungenuine, uniform with, unnatural,
   unreal, utility, utility player, utter, vicar, vicarious,
   vice-president, vice-regent, warped, wear, whited sepulcher