English Etymology From sail + fin. Noun sailfin (plural sailfins) A saillike dorsal fin. Any organism having such a fin, such as a mollie (Poecilia latipinna) or a lizard of the genus Hydrosaurus. Derived terms sailfin cardinalfishsailfin lizardsailfin sandfish Anagrams finialsWikiwand - on Seamless Wikipedia browsing. On steroids.