The Collaborative International Dictionary
Physograde
Physograde \Phys"o*grade\, n. [Gr. ? a bellows + L. gradi to walk, go.] (Zo["o]l.) Any siphonophore which has an air sac for a float, as the Physalia.
Wiktionary
physograde
n. (context zoology English) Any siphonophore which has an air sac for a float.