[sud.den] adj [ME sodain, fr. MF, fr. L subitaneus, fr. subitus sudden, fr. pp. of subire to come up, fr. sub- up + ire to go--more at sub-, issue] (14c) 1 a: happening or coming unexpectedly "a ~ shower" b: changing angle or character all at once
2: marked by or manifesting abruptness or haste
3: made or brought about in a short time: prompt syn see precipitate -- sud.den.ly adv -- sud.den.ness n
[2]sudden n (1559) obs: an unexpected occurrence: emergency -- all of a sudden or on a sudden : sooner than was expected: at once