mercurial
mer-KYOOR-ee-uladjMeaning subject to sudden, unpredictable changes of mood
Memory hook moods as quick as MERCURY. Chef Victor laughs at a joke, roars at a dropped spoon, then hums happily, all in one minute. His moods slip and dart like quick, silvery mercury: he is mercurial.
The mercurial chef was laughing one minute and shouting the next.
In context Working for the mercurial director was exhausting: she praised a scene warmly in the morning and called the same scene a disaster that afternoon.
Similar temperamental, moody, volatile, changeable
Opposite stable, steady, even-tempered
From Latin mercurialis, “of Mercury,” the swift messenger of Roman myth; the quick, slippery liquid metal mercury carries the same name.