UNPREDICTABLE

[adjective] - tending to change suddenly and seemingly without reason and therefore not able to be predicted (= judged in advance) or depended onChanges in the market are, of course, largely unpredictable.The weather there can be a bit unpredictable - one minute it's blue skies and the next minute it's pouring down.Six months before a presidential election, French politics have never looked so unpredictable.The hours in this job are very unpredictable - you sometimes have to work late at very short notice.He was totally unpredictable - you never really knew what he would be like from one day to the next.