abrupt accidental adventitious aleatory casual causeless chance chancy contingent destinal dicey electrifying extraordinary fatal fatidic fluky fortuitous hasty headlong iffy impetuous improbable impulsive incidental indeterminate more than expected nerve-shattering out-of-the-way past expectation precipitant precipitate precipitous quick risky shocking speedy startling sudden surprise surprising swift unannounced unanticipated uncaused undetermined undivined unexpected unforeseeable unguessed unheralded unhoped for unlooked-for unpredictable unpredicted unprepared for unsought without warning