The Collaborative International Dictionary of English v.0.48:

Aggravate \Ag"gra*vate\, v. t. [imp. & p. p. Aggravated; p.
   pr. & vb. n. Aggravating.] [L. aggravatus, p. p. of
   aggravare. See Aggrieve.]
   1. To make heavy or heavier; to add to; to increase. [Obs.]
      "To aggravate thy store." --Shak.
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   2. To make worse, or more severe; to render less tolerable or
      less excusable; to make more offensive; to enhance; to
      intensify. "To aggravate my woes." --Pope.
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            To aggravate the horrors of the scene. --Prescott.
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            The defense made by the prisoner's counsel did
            rather aggravate than extenuate his crime.
                                                  --Addison.
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   3. To give coloring to in description; to exaggerate; as, to
      aggravate circumstances. --Paley.
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   4. To exasperate; to provoke; to irritate. [Colloq.]
      [1913 Webster]

            If both were to aggravate her parents, as my brother
            and sister do mine.                   --Richardson
                                                  (Clarissa).
      [1913 Webster]

   Syn: To heighten; intensify; increase; magnify; exaggerate;
        provoke; irritate; exasperate.
        [1913 Webster]

WordNet (r) 3.0 (2006):

aggravate
    v 1: make worse; "This drug aggravates the pain" [syn: worsen,
         aggravate, exacerbate, exasperate] [ant:
         ameliorate, amend, better, improve, meliorate]
    2: exasperate or irritate [syn: exacerbate, exasperate,
       aggravate]

Moby Thesaurus II by Grady Ward, 1.0:

151 Moby Thesaurus words for "aggravate":
   accelerate, agent provocateur, aggrandize, alienate, amplify,
   anger, annoy, antagonize, arouse, augment, badger, bait, be at,
   bedevil, beef up, beset, blow up, bother, bristle, brown off, bug,
   build up, bullyrag, burn up, chafe, chivy, come between,
   complicate, concentrate, condense, consolidate, damage, deepen,
   deteriorate, devil, dilapidate, disaffect, discompose, distemper,
   disturb, disunite, divide, dog, double, embitter, endamage,
   enhance, enlarge, envenom, estrange, exacerbate, exaggerate,
   exasperate, exercise, fan the flame, fash, fret, frustrate, gall,
   get, grate, gripe, harass, harm, harry, heat up, heckle, hector,
   heighten, hop up, hot up, hound, huff, hurt, impair, incense,
   increase, inflame, infuriate, injure, intensify, irk, irritate,
   jazz up, key up, light the fuse, madden, magnify, make acute,
   make complex, make trouble, make worse, miff, molest, mount,
   multiply, nag, needle, nettle, nudzh, peeve, persecute, perturb,
   pester, pick on, pique, pit against, plague, pluck the beard,
   pother, provoke, put back, ramify, rankle, redouble, reinforce,
   ride, rile, rise, roil, rouse, ruffle, separate, set against,
   set at odds, set at variance, set on, set up, sharpen, sic on,
   soup up, sour, sow dissension, step up, stir the blood, stir up,
   stir up trouble, strengthen, tease, torment, triple, trouble,
   try the patience, tweak the nose, upset, vex, weaken, whet,
   work up, worry, worsen