I. (ˌ)mər-ˈkyu̇r-ē-əl adjective
Date: 14th century
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
Synonyms: see inconstant
• mer·cu·ri·al·ly -ē-ə-lē adverb
• mer·cu·ri·al·ness noun
II. noun
Date: 1676
: a pharmaceutical or chemical containing mercury