Sudden

a.	1.	Happening without previous notice or with very brief notice; coming unexpectedly, or without the common preparation; immediate; instant; speedy. Sudden fear troubleth thee. - Job xxii. 10.
	2.	Hastly prepared or employed; quick; rapid. Never was such a sudden scholar made. - Shak. The apples of Asphaltis, appearing goodly to the sudden eye. - Milton.
	3.	Hasty; violent; rash; precipitate.
adv.	1.	Suddenly; unexpectedly. Herbs of every leaf that sudden flowered. - Milton.
n.	1.	An unexpected occurrence; a surprise. All of a sudden sooner than was expected; without the usual preparation; suddenly. How art thou lost! how on a sudden lost! - Milton. He withdrew his opposition all of a sudden. - Thackeray.

Adj.

1.

sudden - happening without warning or in a short space of time; "a sudden storm"; "a sudden decision"; "a sudden cure" Antonyms: gradual - proceeding in small stages; "a gradual increase in prices"

aback, abruptly, accelerated, breakneck, breathless, brisk, electrifying, expeditious, extraordinary, fast, fleet, forthwith, hasty, headlong, hurried, impatient, impetuous, improbable, impulsive, more than expected, nerve-shattering, out-of-the-way, overhasty, panting, past expectation, precipitant, precipitate, precipitous, quick, rash, reckless, rushing, shocking, short, speedy, startling, suddenly, surprising, unannounced, unanticipated, unanticipatedly, unaware, undivined, unexpectedly, unforeseeable, unguessed, unheralded, unhoped for, unlooked-for, unpredictable, unpredicted, unprepared for, unwonted, without warning