zygomorphoushttp://www.oed.com/dictionary/zygomorphous_adj%3Ftab%3Dmeaning_and_usezygomorphous, adj.
First published 1921; not fully revised

zygomorphousadjective

Botany.
  1. 1879–
    Stressed as zygoˈmorphous.
    1. 1879
      Both these forms [sc. monosymmetrical and polysymmetrical] have a more expressive and older terminology, adopted by Eichler, viz.:—Zygomorphous, for flowers, or other structures, which can be bisected in one plane,..(median zygomorphous, when this is a median or anteroposterior plane,..transverse zygomorphous, when the plane of section is transverse or at right angles to the median).
      A. Gray in A. Gray & G. L. Goodale, Botanical Text-book (ed. 6) vol. I. 175 (note)

Originally published as part of the entry for zygomorphic, adj.

zygomorphic, adj. was first published in 1921; not fully revised.