Erratic

1. adjective

   likely to perform unpredictably; ; ; - Osbert Lancaster

   “erratic winds are the bane of a sailor”

   Similar: temperamental

2. adjective

   liable to sudden unpredictable change

   “erratic behavior”

   Similar: fickle, mercurial, quicksilver

3. adjective

   having no fixed course

   “an erratic comet”

   Similar: planetary, wandering