The Collaborative International Dictionary of English v.0.48:

Gonochorism \Gon`o*cho"rism\, n. [Gr. ? offspring + ? to
   separate.]
   (a) Separation of the sexes in different individuals; --
       opposed to hermaphroditism.
   (b) In ontogony, differentiation of male and female
       individuals from embryos having the same rudimentary
       sexual organs.
   (c) In phylogeny, the evolution of distinct sexes in species
       previously hermaphrodite or sexless.
       [1913 Webster]