1. (

• mercury ,
• quicksilver ,
• hydrargyrum ,
• Hg ,
• atomic_number_ ,

) a heavy silvery toxic univalent and bivalent metallic element; the only metal that is liquid at ordinary temperatures ;

1. (

• erratic ,
• fickle ,
• mercurial ,
• quicksilver

) liable to sudden unpredictable change; "erratic behavior"; "fickle weather"; "mercurial twists of temperament"; "a quicksilver character, cool and willful at one moment, utterly fragile the next" ;