The Collaborative International Dictionary of English v.0.48:

Incongruent \In*con"gru*ent\, a. [L. incongruens. See In- not,
   and Congruent.]
   Incongruous. --Sir T. Elyot.
   [1913 Webster]

WordNet (r) 3.0 (2006):

incongruent
    adj 1: not congruent [ant: congruent]