The Collaborative International Dictionary of English v.0.48:

Congruous \Con"gru*ous\, a. [L. congruus, fr. congruere to come
   together, to coincide, to agree. Of uncertain origin.]
   Suitable or concordant; accordant; fit; harmonious;
   correspondent; consistent.
   [1913 Webster]

         Not congruous to the nature of epic poetry. --Blair.
   [1913 Webster]

         It is no ways congruous that God should be always
         frightening men into an acknowledgment of the truth.
                                                  --Atterbury.
   [1913 Webster]

WordNet (r) 3.0 (2006):

congruous
    adj 1: corresponding in character or kind [syn: congruous,
           congruent] [ant: incongruous]
    2: suitable or appropriate together

Moby Thesaurus II by Grady Ward, 1.0:

89 Moby Thesaurus words for "congruous":
   accordant, advantageous, advisable, affirmative, agreeable,
   agreeing, answerable, appropriate, at one, becoming, befitting,
   coexistent, coexisting, coherent, coincident, coinciding,
   commensurate, compatible, concordant, concurring, conformable,
   congenial, congruent, consentaneous, consentient, consistent,
   consonant, convenient, cooperating, cooperative, correspondent,
   corresponding, decent, desirable, en rapport, equivalent,
   expedient, favorable, feasible, felicitous, fit, fitten, fitting,
   fructuous, good, happy, harmonious, in accord, in agreement,
   in rapport, in sync, in synchronization, inaccordance, inharmony,
   like-minded, likely, meet, of a piece, of like mind, of one mind,
   on all fours, opportune, politic, positive, profitable, proper,
   proportionate, recommendable, reconcilable, right, seasonable,
   seemly, self-consistent, sortable, suitable, symbiotic,
   sympathetic, synchronized, synchronous, timely, to be desired,
   unanimous, uniform, unisonant, unisonous, useful, well-timed, wise,
   worthwhile