mercurial – changeable; changing suddenly and often

(Pronounced muh-kyoo-ree-uhl)

To remember the definition of the word mercurial, use the following mnemonic:

The mercury in the thermometer all (mercurial) of a sudden dropped. The weather in this area can change suddenly and often.

Examples of mercurial in a sentence

His mercurial temperament made him difficult to work with.  

The weather here is so mercurial, you need to be prepared for every season. 

They had a mercurial relationship that seemed to end every other day.