Entry 1 sense Webster, 1913 Oostegite · O·os·te·gite · IPA /oʊˈ(w)ɑstɪˌd͡ʒaɪt/ 01 n. One of the plates which in some Crustacea inclose a cavity wherein the eggs are hatched. 1. One of the plates which in some Crustacea inclose a cavity wherein the eggs are hatched.(Zool.)