cerulean /səˈɹuːli.ən/noun 2adjective 1forms 3 noun2 •A greenish-blue color.For our blues we have the azures and ceruleans, lapis lazulis, the light and dusty, the powder blues, the deeps: royal, sapphire, navy, and marine […] — 2014 •Any of various lycaenid butterflies of the genus Jamides. adjective1 •Sky-blue.As far to the west as Monica could see, her world was a sea of fog, […]. Above it arched a cerulean sky; as the sun climbed to the zenith, […], the fog gradually took on a bluish tinge. — 1920 formsceruleans · more cerulean · most cerulean