Definition of "mercurial" []

• Roman Mythology Of or relating to the god Mercury. (adjective)
• Astronomy Of or relating to the planet Mercury. (adjective)
• Having the characteristics of eloquence, shrewdness, swiftness, and thievishness attributed to the god Mercury. (adjective)
• Containing or caused by the action of the element mercury. (adjective)
• Quick and changeable in temperament; volatile: a mercurial nature. (adjective)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "I guess the "mercurial" is a pretty negative thing."
• "Jobs is often described as mercurial and prone to outbursts, while Cook, who was raised in a small town in Alabama, is polite and soft-spoken, The Times reports."
• "A number of people have described Denny as "mercurial" - the commanding personality who was sometimes afraid to go onstage."