The Collaborative International Dictionary of English v.0.48:

Dissatisfy \Dis*sat"is*fy\, v. t. [imp. & p. p. Dissatisfied;
   p. pr. & vb. n. Dissatisfying.]
   To render unsatisfied or discontented; to excite uneasiness
   in by frustrating wishes or expectations; to displease by the
   want of something requisite; as, to be dissatisfied with
   one's fortune.
   [1913 Webster]

         The dissatisfied factions of the autocracy. --Bancroft.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dissatisfy
    v 1: fail to satisfy [ant: gratify, satisfy]

Moby Thesaurus II by Grady Ward, 1.0:

21 Moby Thesaurus words for "dissatisfy":
   baffle, balk, bilk, cast down, cross, dash, defeat,
   defeat expectation, disappoint, discontent, disgruntle, dishearten,
   disillusion, displease, foil, frustrate, let down, put out,
   tantalize, tease, thwart