Defn: A radical regarded as derived from ammonium by the substitution of mercury for a portion of the hydrogen.
MERCURIAL Mer*cu"ri*al, a. Etym: [L. mercurialis, fr. Mercurius Mercury: cf. F. mercuriel.]
1. Having the qualities fabled to belong to the god Mercury; swift; active; sprightly; fickle; volatile; changeable; as, a mercurial youth; a mercurial temperament. A mercurial man Who fluttered over all things like a fan. Byron.
2. Having the form or image of Mercury; — applied to ancient guideposts. [Obs.] Chillingworth.
3. Of or pertaining to Mercury as the god of trade; hence, money- making; crafty. The mercurial wand of commerce. J. Q. Adams.
4. Of or pertaining to, or containing, mercury; as, mercurial preparations, barometer. See Mercury, 2.
5. (Med.)
Defn: Caused by the use of mercury; as, mercurial sore mouth.
MERCURIAL
Mer*cu"ri*al, n.
1. A person having mercurial qualities. Bacon.