The Collaborative International Dictionary of English v.0.48:

Consonance \Con"so*nance\, Consonancy \Con"so*nan*cy\, n. [L.
   consonantia: cf. F. consonnance.]
   1. (Mus.) Accord or agreement of sounds produced
      simultaneously, as a note with its third, fifth, and
      eighth.
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   2. Agreement or congruity; harmony; accord; consistency;
      suitableness.
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            The perfect consonancy of our persecuted church to
            the doctrines of Scripture and antiquity. --Hammond.
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            The optic nerve responds to the waves with which it
            is in consonance.                     --Tyndall.
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   3. Friendship; concord. [Obs.]
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            By the consonancy of our youth.       --Shak.

   Syn: Agreement; accord; consistency; unison; harmony;
        congruity; suitableness; agreeableness.
        [1913 Webster]

WordNet (r) 3.0 (2006):

consonance
    n 1: the repetition of consonants (or consonant patterns)
         especially at the ends of words [syn: consonance,
         consonant rhyme]
    2: the property of sounding harmonious [syn: consonance,
       harmoniousness]