The Collaborative International Dictionary of English v.0.48:

Complicate \Com"pli*cate\, a. [L. complicatus, p. p. of
   complicare to fold together. See Complex.]
   1. Composed of two or more parts united; complex;
      complicated; involved.
      [1913 Webster]

            How poor, how rich, how abject, how august,
            How complicate, how wonderful is man! --Young.
      [1913 Webster]

   2. (Bot.) Folded together, or upon itself, with the fold
      running lengthwise.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Complicate \Com"pli*cate\, v. t. [imp. & p. p. Complicated; p.
   pr. & vb. n. Complicating.]
   To fold or twist together; to combine intricately; to make
   complex; to combine or associate so as to make intricate or
   difficult.
   [1913 Webster]

         Nor can his complicated sinews fail.     --Young.
   [1913 Webster]

         Avarice and luxury very often become one complicated
         principle of action.                     --Addison.
   [1913 Webster]

         When the disease is complicated with other diseases.
                                                  --Arbuthnot.
   [1913 Webster]

WordNet (r) 3.0 (2006):

complicate
    v 1: make more complicated; "There was a new development that
         complicated the matter" [syn: complicate, perplex]
         [ant: simplify]
    2: make more complex, intricate, or richer; "refine a design or
       pattern" [syn: complicate, refine, rarify, elaborate]

Moby Thesaurus II by Grady Ward, 1.0:

95 Moby Thesaurus words for "complicate":
   accelerate, add, adjoin, affix, agglutinate, aggravate, annex,
   append, attach, ball up, beef up, blow up, burden, concentrate,
   condense, confound, confuse, conjoin, consolidate, decorate,
   deepen, derange, disarrange, disorder, double, embrangle, encumber,
   enhance, entangle, exacerbate, exaggerate, foul up, garble,
   glue on, heat up, heighten, hitch on, hop up, hot up, implicate,
   infix, intensify, involve, jazz up, join with, jumble, key up,
   knot, louse up, magnify, make complex, make unintelligible,
   mess up, mix up, muck, muck up, muddle, mystify, obfuscate,
   obscure, ornament, paste on, perplex, plus, postfix, prefix,
   put with, ramify, ravel, redouble, reinforce, saddle with,
   scramble, screw up, shadow, sharpen, slap on, snafu, snarl,
   snarl up, soup up, step up, strengthen, subjoin, suffix, superadd,
   superpose, tack on, tag, tag on, tangle, triple, unite with, upset,
   whet