Mercurial

 WORD OF THE DAY

mercurial / adjective / mer-KYUR-ee-ul 

Definition

1: of, relating to, or born under the planet Mercury
2: having qualities of eloquence, ingenuity, or thievishness attributed to the god Mercury or to the influence of the planet Mercury
3: characterized by rapid and unpredictable changeableness of mood
4: of, relating to, containing, or caused by mercury

Examples
"But Cabrera was the definition of mercurial. He might be yelling at the top of his lungs, playfully arguing with a teammate, then quickly turn sullen when approached by a reporter."

— Carlos Monarrez, The Detroit Free Press, 26 Apr. 2022

Some scientists suggest that because manic-depressive patients are ever riding the bio-chemical express between emotional extremes, their brains end up more complexly wired and remain more persistently plastic than do the brains of less mercurial sorts.
— Natalie Angier, New York Times, 12 Oct. 1993

Did You Know?
The Roman god Mercury (Mercurius in Latin) was the messenger and herald of the gods and also the god of merchants and thieves (his counterpart in Greek mythology is Hermes).
He was noted for his eloquence, swiftness, and cunning, and the Romans named what appeared to them to be the fastest-moving planet in his honor.
The Latin adjective derived from his name, mercurialis, meaning "of or relating to Mercury," was borrowed into English in the 14th century as mercurial.
Although the adjective initially meant "born under the planet Mercury," it came to mean "having qualities attributed to the god Mercury or the influence of the planet Mercury," and then "unpredictably changeable."