1. 善变的;变化无常的;难以预测的
If you describe someone as mercurial, you mean that they frequently change their mind or mood without warning.

1. liable to sudden unpredictable change

e.g. erratic behavior
fickle weather
mercurial twists of temperament
a quicksilver character, cool and willful at one moment, utterly fragile the next

Synonym: erraticficklequicksilver(a)

2. relating to or containing or caused by mercury

e.g. mercurial preparations
mercurial sore mouth