Synonyms:
erratic, fickle, mercurial, quicksilver(a)
Meaning: 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"
Usage examples
We had to steer more and more to the west, so that our course was very erratic.
Slowly she swung from her course, circling back toward us in an erratic and pitiful manner.
There was little change in the formation of the gorge; it still wound its erratic course between precipitous cliffs.
Divided councils caused our course to be erratic after this, and finally, at 9 P.M. we landed in the worst place of all.
So chaotic and erratic had been the household service, and so quietly did Billy slip into her new role, that it was not until the second meal after the maid's departure that the master of the house discovered what had happened.