Placophora /(plȧ*kŏf"ō̇*rȧ)/ Pla·coph·o·ra Placophora n. pl. A division of gastropod Mollusca, including the chitons. The back is covered by eight shelly plates. Called also Polyplacophora. See Illust. under Chiton, and Isopleura. (Zool.)