1. Having the qualities fabled to belong to the god mercury; swift; active; sprightly; fickle; volatile; changeable; as, a mercurial youth; a mercurial temperament. A mercurial man who fluttered over all things like a fan. (Byron)
Origin: L. Mercurialis, fr. Mercurius Mercury: cf. F. Mercuriel.
1. A person having mercurial qualities.