Source : Webster's Revised Unabridged Dictionary (1913)

Zygomorphic \Zyg`o*mor"phic\, Zygomorphous \Zyg`o*mor"phous\, a.
   [Gr. ? a yoke + ? form.] (Biol.)
   Symmetrical bilaterally; -- said of organisms, or parts of
   organisms, capable of division into two symmetrical halves
   only in a single plane.

Source : WordNet®

zygomorphous
     adj : capable of division into symmetrical halves by only one
           longitudinal plane passing through the axis [syn: {zygomorphic},
            {bilaterally symmetrical}] [ant: {actinomorphic}]