Synonyms: unpredictable, irregular
Definition: not occurring at expected times
Similar words: sporadic
Definition: recurring in scattered and irregular or unpredictable instances
Usage: a city subjected to sporadic bombing raids
Synonyms: unpredictable
Definition: unknown in advance
Usage: an unpredictable (or indeterminable) future
Similar words: undeterminable, indeterminable
Definition: not capable of being definitely decided or ascertained
Synonyms: unpredictable
Definition: not capable of being foretold
Similar words: aleatory
Definition: dependent on chance
Usage: the aleatory element in life
Similar words: capricious, freakish
Definition: changeable
Usage: a capricious summer breeze; freakish weather
Similar words: episodic, occasional
Definition: occurring or appearing at usually irregular intervals
Usage: episodic in his affections; occasional headaches
Similar words: unforeseeable
Definition: incapable of being anticipated
Usage: unforeseeable consequences