The Collaborative International Dictionary of English v.0.48:

Agonize \Ag"o*nize\, v. i. [imp. & p. p. Agonized; p. pr. &
   vb. n. Agonizing.] [F. agoniser, LL. agonizare, fr. Gr. ?.
   See Agony.]
   1. To writhe with agony; to suffer violent anguish.
      [1913 Webster]

            To smart and agonize at every pore.   --Pope.
      [1913 Webster]

   2. To struggle; to wrestle; to strive desperately.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Agonize \Ag"o*nize\, v. t.
   To cause to suffer agony; to subject to extreme pain; to
   torture.
   [1913 Webster]

         He agonized his mother by his behavior.  --Thackeray.
   [1913 Webster]

WordNet (r) 3.0 (2006):

agonize
    v 1: cause to agonize [syn: agonize, agonise]
    2: suffer agony or anguish [syn: agonize, agonise]

Moby Thesaurus II by Grady Ward, 1.0:

118 Moby Thesaurus words for "agonize":
   ache, afflict, agonize over, ail, anguish, battle, be at sea,
   be uncertain, bear, beat about, bite, blanch, bleed, blench,
   bloody, brood over, buffet, burn, chafe, claw, contend, convulse,
   crucify, cut, desolate, distress, doubt, endure, excruciate,
   feel pain, feel the pangs, feel unsure, fester, fight, flounder,
   fret, gall, give pain, gnaw, go hard with, grate, grieve, grimace,
   grind, gripe, grope, grunt and sweat, harrow, hassle,
   have a misery, huff and puff, hurt, impale, inflame, inflict pain,
   irritate, kill by inches, lacerate, lancinate, macerate, martyr,
   martyrize, mope, mourn, nip, pain, pierce, pinch, pine, pine away,
   pound, prick, prolong the agony, punish, put to torture,
   puzzle over, question, rack, rankle, rasp, rip, rub, savage,
   scarify, scuffle, shoot, shrink, smart, sorrow, squirm, stab,
   sting, strive, struggle, suffer, suffer anguish, take on,
   thrash about, thrill, throb, tingle, torment, torture, toss,
   trouble, try, tussle, tweak, twinge, twist, twitch, wince, wonder,
   wonder whether, wound, wrestle, wring, writhe