[mer.cu.ri.al] adj (14c) 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
4: of, relating to, containing, or caused by mercury syn see inconstant -- mer.cu.ri.al.ly adv -- mer.cu.ri.al.ness n
[2]mercurial n (1676): a pharmaceutical or chemical containing mercury