The Collaborative International Dictionary of English v.0.48:

Dissuade \Dis*suade"\, v. t. [imp. & p. p. Dissuaded; p. pr. &
   vb. n. Dissuading.] [L. dissuadere, dissuasum; dis- +
   suadere to advise, persuade: cf. F. dissuader. See
   Suasion.]
   1. To advise or exhort against; to try to persuade (one from
      a course). [Obsolescent]
      [1913 Webster]

            Mr. Burchell, on the contrary, dissuaded her with
            great ardor: and I stood neuter.      --Goldsmith.
      [1913 Webster]

            War, therefore, open or concealed, alike
            My voice dissuades.                   --Milton.
      [1913 Webster]

   2. To divert by persuasion; to turn from a purpose by reasons
      or motives; -- with from; as, I could not dissuade him
      from his purpose.
      [1913 Webster]

            I have tried what is possible to dissuade him.
                                                  --Mad. D'
                                                  Arblay.
      [1913 Webster]

WordNet (r) 3.0 (2006):

dissuade
    v 1: turn away from by persuasion; "Negative campaigning will
         only dissuade people" [syn: dissuade, deter] [ant:
         persuade]

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "dissuade":
   admonish, advise, caution, counsel, cry out against, daunt, derail,
   deter, discourage, divert, exhort, expostulate, frighten off,
   intimidate, kid out of, prick, remonstrate, talk out of, throw off,
   unpersuade, urge, warn