"erratic" in the adjective sense
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"
2. erratic, planetary, wandering
having no fixed course
"an erratic comet"
"his life followed a wandering course"
"a planetary vagabond"
3. erratic, temperamental
likely to perform unpredictably sometimes it would start and sometimes it wouldn't"
"erratic winds are the bane of a sailor"
"a temperamental motor
"that beautiful but temperamental instrument the flute"- Osbert Lancaster
Source: WordNet® (An amazing lexical database of English)
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