The Collaborative International Dictionary of English v.0.48:
Unfertile \Un*fer"tile\, a. Not fertile; infertile; barren. -- Un*fer"tile*ness, n. [1913 Webster]WordNet (r) 3.0 (2006):
unfertile adj 1: incapable of reproducing; "an infertile couple" [syn: sterile, unfertile, infertile] [ant: fertile]