Definition of mercurials:
(adj) :
(comparable) Having a lively or volatile character; animated, changeable, quick-witted.
(n) :
(astrology) A person born under the influence of the planet Mercury; hence, a person having an eloquent, quickwitted, furtive, or volatile character.
(n) :
(chemistry) A chemical compound containing mercury.
(adj) :
(not comparable, chemistry) Of or pertaining to the element mercury or quicksilver; containing mercury.
(adj) :
(not comparable, medicine) Caused by the action of mercury or a mercury compound.
(adj) :
(not comparable, astrology) Pertaining to the astrological influence of the planet Mercury; having the characteristics of a person under such influence (see adjective sense 1).