quick‧sil‧ver /ˈkwɪkˌsɪlvə $ -ər/
noun [uncountable]1. old use the metal
mercury2. literary something that is like quicksilver changes or moves quickly in a way that you do not expect:
His mood changed like quicksilver.—quicksilver adjective:
his quicksilver temperament [TahlilGaran] Dictionary of Contemporary English ▲