erratic

adjective

1. 1

   liable to sudden unpredictable change

   erratic behavior

   fickle weather

2. 2

   likely to perform unpredictably

   erratic winds are the bane of a sailor

   a temperamental motor; sometimes it would start and sometimes it wouldn't

3. 3

   having no fixed course

   an erratic comet

   his life followed a wandering course