The Collaborative International Dictionary of English v.0.48:

Plagiarize \Pla"gia*rize\, v. t. [imp. & p. p. Plagiarized; p.
   pr. & vb. n. Plagiarizing.]
   To steal or purloin from the writings of another; to
   appropriate without due acknowledgement (the ideas or
   expressions of another).
   [1913 Webster]

WordNet (r) 3.0 (2006):

plagiarize
    v 1: take without referencing from someone else's writing or
         speech; of intellectual property [syn: plagiarize,
         plagiarise, lift]

Moby Thesaurus II by Grady Ward, 1.0:

53 Moby Thesaurus words for "plagiarize":
   act like, adopt, affect, appropriate, assume, borrow, chorus,
   come again, copy, counterfeit, crib, derive from, ditto, do,
   do a repeat, do again, do like, do over, double, duplicate, echo,
   fake, forge, go like, hoke, hoke up, imitate, infringe,
   infringe a copyright, make like, make use of, mirror, mock, parrot,
   pirate, quote, redo, redouble, reduplicate, reecho, reflect,
   regurgitate, reincarnate, renew, repeat, reproduce, revive,
   say again, simulate, steal, take, take on, take over



The Devil's Dictionary (1881-1906):

PLAGIARIZE, v.  To take the thought or style of another writer whom
one has never, never read.