mercurial

/mɝkˈjʊɹiəɫ/

subject to sudden or unpredictable changes of mood or mind

mercurial in a sentence

“His mercurial temperament kept everyone on edge.”

From Mercury, the swift Roman messenger god

Related Words

saturnine

slow and gloomy; dark in coloring and moody

stoic

enduring pain and hardship without showing feelings

laconic

using very few words

stentorian

loud and powerful (of a voice)

spartan

showing indifference to comfort or luxury; austere

draconian

excessively harsh and severe (usually laws)