MERCURIAL

I. adjective Date: 14th century of, relating to, or born under the planet Mercury, having qualities of eloquence, ingenuity, or thievishness attributed to the god Mercury or to the influence of the planet Mercury, characterized by rapid and unpredictable changeableness of mood , of, relating to, containing, or caused by mercury, see: inconstant ~ly adverb ~ness noun II. noun Date: 1676 a pharmaceutical or chemical containing mercury