unifacial

from WordNet (r) 3.0 (2006)

unifacial
    adj 1: having but one principal or specialized surface; "a
           primitive unifacial flint tool"

from The Collaborative International Dictionary of English v.0.48

Unifacial \U`ni*fa"cial\, a. [Uni- + facial.]
   Having but one front surface; as, some foliaceous corals are
   unifacial, the polyp mouths being confined to one surface.
   [1913 Webster]