Entry 1 sense Webster, 1913 Plagiostomi · Pla·gi·os·to·mi · IPA 01 n. pl. An order of fishes including the sharks and rays; -- called also Plagiostomata. 1. An order of fishes including the sharks and rays; -- called also Plagiostomata.(Zool.) Also: <ord>Plagiostomata</ord>