The Collaborative International Dictionary of English v.0.48:

Uncustomary \Uncustomary\
   See customary.

Moby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "uncustomary":
   breakaway, extraordinary, offbeat, rare, recherche, singular,
   sui generis, uncommon, undreamed-of, unexpected, unfamiliar,
   unheard-of, unique, unordinary, unthinkable, unthought-of, unusual,
   unwonted