The Collaborative International Dictionary of English v.0.48:

Syncopate \Syn"co*pate\, v. t. [imp. & p. p. Syncopated; p.
   pr. & vb. n. Syncopating.] [LL. syncopatus, p. p. of
   syncopare to syncopate, to swoon. See Syncope.]
   1. (Gram.) To contract, as a word, by taking one or more
      letters or syllables from the middle; as, "Gloster" is a
      syncopated form of "Gloucester."
      [1913 Webster]

   2. (Mus.) To commence, as a tone, on an unaccented part of a
      measure, and continue it into the following accented part,
      so that the accent is driven back upon the weak part and
      the rhythm drags.
      [1913 Webster]

WordNet (r) 3.0 (2006):

syncopated
    adj 1: stressing a normally weak beat