tem·per·a·men·tal /ËŒtemp(É™)rəˈmen(t)l/ Learn to pronounce adjective 1. (of a person) liable to unreasonable changes of mood. synonyms: volatile, excitable, emotional, overemotional, mercurial, capricious, erratic, unpredictable, changeable, inconsistent, unstable, hotheaded, fiery, explosive, hot-tempered, short-tempered, quick-tempered, irritable, irascible, impatient, petulant, prima donna-ish, melodramatic.