DelphinusPronunciation: /dɛlˈfʌɪnəs/ AstronomyDefinition of Delphinus a small constellation (the Dolphin), just north of the celestial equator near Cygnus. (as genitive Delphini /dɛlˈfʌɪni/) used with preceding letter or numeral to designate a star in this constellation:the star Alpha DelphiniOrigin:LatinDelphinus in other Oxford dictionaries Definition of Delphinus in the US English dictionary