The Collaborative International Dictionary of English v.0.48:

Dioecian \Di*[oe]"cian\, Dioecious \Di*[oe]"cious\, a. (Biol.)
   Having the sexes in two separate individuals; -- applied to
   plants in which the female flowers occur on one individual
   and the male flowers on another of the same species, and to
   animals in which the ovum is produced by one individual and
   the sperm cell by another; -- opposed to mon[oe]cious.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dioecious
    adj 1: having male and female reproductive organs in separate
           plants or animals [syn: dioecious, dioecian] [ant:
           monecious, monoecious, monoicous]