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]