any of an order (Siphonophora) of small, transparent, often colored, swimming or floating sea hydrozoans composed of several kinds of polyps and including the Portuguese man-of-war
See siphonophore in American Heritage Dictionary 4
(sī-fŏnˈə-fôrˌ, -fōrˈ, sīˈfə-nə-)
noun
Any of various transparent, often subtly colored marine hydrozoans of the order Siphonophora, consisting of a floating or swimming colony of polyplike and medusalike individuals and including the Portuguese man-of-war.