The Collaborative International Dictionary of English v.0.48:

Unanimity \U`na*nim"i*ty\, n. [L. unanimitas: cf. F.
   unanimit['e].]
   The quality or state of being unanimous.
   [1913 Webster]

WordNet (r) 3.0 (2006):

unanimity
    n 1: everyone being of one mind

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "unanimity":
   acclamation, accord, accordance, agreement, agreement of all,
   chorus, common assent, common consent, concert, concord,
   concordance, concurrence, confluence of minds, consensus,
   consensus gentium, consensus of opinion, consensus omnium, consent,
   consentaneity, general acclamation, general agreement,
   general consent, general voice, harmony, like-mindedness,
   meeting of minds, mutual understanding, one accord, one voice,
   same mind, single voice, total agreement, unanimousness,
   understanding, unison, universal agreement