Happening when the other person had done nothing to cause it. This is the word English uses to place blame cleanly: an unprovoked attack means the victim did not start it, did not threaten, did not insult anyone first. It goes most naturally with attack, assault, violence, aggression, anger, and — very often — animals: an unprovoked shark attack, an unprovoked dog bite. Behind it sits an old assumption worth noticing: that violence usually HAS a cause, that people hit back rather than hit first, so it needs saying specially when there was no cause at all. That is why the word carries such weight in news reports and courtrooms. It nearly always sits in front of a noun ("an unprovoked assault") or after a linking verb ("the attack was unprovoked"). A milder everyday use exists for sudden bad moods — "an unprovoked outburst" from a normally calm person — where nobody is hurt but the same idea holds: it came from nowhere.