thick-walled spore that develops from an oosphere through either fertilzation or parthenogenesis.

A sexual spore produced by a the union of two morphologically different gametangia (oogonium and antheridium). Thick-walled, sexually-derived resting spore of oomycete fungi.

(Gr. ôon: egg; sporä seed) n. A zygote that is produced as a result of oogamy in certain algae and fungi, corresponding to angiosperm seeds. It contains food reserves, develops a protective outer covering, and enters a resting phase before germination. Cf. zygospore. Also oöspore.