Pronunciation: (mur-kyoor'ē-ul),[key] —adj. 1. changeable; volatile; fickle; flighty; erratic: a mercurial nature. 2. animated; lively; sprightly; quick-witted.
3. pertaining to, containing, or caused by the metal mercury.
4. (cap.) of or pertaining to the god Mercury.
5. ( cap.) of or pertaining to the planet Mercury.
—n. Pharm.a preparation of mercury used as a drug.