The Collaborative International Dictionary of English v.0.48:

Infertile \In*fer"tile\, a. [L. infertilis: cf. F. infertile.
   See In- not, and Fertile.]
   Not fertile; not productive; barren; sterile; unable to
   propagate its kind; as, an infertile soil; an infertile
   hybrid; -- of living things and of soil or land.
   [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

infertile
    adj 1: incapable of reproducing; "an infertile couple" [syn:
           sterile, unfertile, infertile] [ant: fertile]

Moby Thesaurus II by Grady Ward, 1.0:

65 Moby Thesaurus words for "infertile":
   acarpous, arid, barren, celibate, childless, depleted, desert,
   desolate, drained, dried-up, dry, dull, earthbound, effete,
   exhausted, fallow, fruitless, gaunt, gelded, impotent,
   impoverished, ineffectual, infecund, issueless, jejune, leached,
   literal, menopausal, mundane, nonfertile, nonproducing,
   nonproductive, nonprolific, parasitize, prosaic, prosing, prosy,
   sine prole, staid, sterile, stolid, stuffy, sucked dry, teemless,
   uncultivated, unfanciful, unfertile, unfruitful, unideal,
   unimaginative, uninspired, uninventive, unoriginal, unplowed,
   unpoetic, unproductive, unprolific, unromantic, unromanticized,
   unsown, untilled, virgin, waste, wasted, without issue