diœcia

from The Century Dictionary.

• The twenty-second class of plants in the artificial system of Linnæus.

from the GNU version of the Collaborative International Dictionary of English.

• noun plural (Bot.) A Linnæan class of plants having the stamens and pistils on different plants.
• noun plural (Zoöl.) A subclass of gastropod mollusks in which the sexes are separate. It includes most of the large marine species, like the conchs, cones, and cowries.