Marine; oceanic; of or inhabiting the deep or open sea: said of those aquatic plants and animals which inhabit the high seas. Also Pelagian.Specifically, in marine biol.: Living at the surface of the high sea at a distance from land.Living at the surface of the sea. See the extract.Living at the surface of the water, either salt or fresh.Floating or swimming in the water, either at the surface or at any depth below it.In geology and geography, of or pertaining to the deep ocean; far from land.