Portuguese man-of-war /por′chəgēs/ , any member of the genus Physalia, in the phylum Cnidaria. All species have a large purple air sac that allows them to float on the surface of the water, and from which many long tentacles of stinging polyps hang. The tentacles are equipped with nematocysts that are able to penetrate the skin of humans, causing intense pain. Paralysis can result from numerous stings.
