The Collaborative International Dictionary of English v.0.48:

Unopposed \Unopposed\
   See opposed.

WordNet (r) 3.0 (2006):

unopposed
    adj 1: not having opposition or an opponent; "unopposed military
           forces"; "the candidate was unopposed" [ant: opposed]

Moby Thesaurus II by Grady Ward, 1.0:

20 Moby Thesaurus words for "unopposed":
   agreeing, at one, at one with, carried by acclamation, concordant,
   concurrent, consentaneous, in agreement, like-minded, of a piece,
   of one accord, of one mind, solid, unanimous, unchallenged,
   uncontested, uncontradicted, uncontroverted, with one consent,
   with one voice