Definition of mercurial
(Entry 1 of 2)
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
a mercurial temper
4
: of, relating to, containing, or caused by mercury
mercurial
nounDefinition of mercurial (Entry 2 of 2)
: a pharmaceutical or chemical containing mercury
Test Your Vocabulary
The Great British Vocabulary Quiz
-
- Named after Sir Robert Peel, what are British police called?

Test your vocabulary with our 10-question quiz!
TAKE THE QUIZ
A daily challenge for crossword fanatics.
TAKE THE QUIZLove words? Need even more definitions?
Merriam-Webster unabridged
Share mercurial
Time Traveler for mercurial
The first known use of mercurial was in the 14th century
See more words from the same century