Synonyms for Sudden:

adj.

dramatic (adjective)
sensational.
sudden (adjective)
unexpected, precipitous, instantaneous, hasty, abrupt, quick, immediate.
surprising (adjective)
shocking, astonishing, astounding, unforeseen, unexpected, startling, surprising, unanticipated.
unexpected; happening quickly (adjective)
fast, precipitate, precipitous, impromptu, abrupt, precipitant, swift, immediate, unforeseen, hurried, hasty, quick.
very fast (adjective)
swift.

n.

earth-shattering, sensational, remarkable, extraordinary, amazing, staggering, phenomenal. precipitant, surprise, precipitate, fast, hurried. precipitate (noun)
swift, unfore, impromptu.
sudden (noun)
abrupt, fulminant, unforeseen, explosive, sharp, unexpected.

Other synonyms:

hurried, precipitant. precipitate. flying
swift.
Other relevant words:
staggering, fast, swift, impromptu, earth-shattering, amazing, precipitate, sharp, remarkable, precipitant, fulminant, phenomenal, sensational, surprise, hurried, extraordinary, explosive, unfore.

Usage examples for sudden

  1. " Forgive me," he begged, with a sudden change of voice. – The Zeppelin's Passenger by E. Phillips Oppenheim
  2. He gave a sudden start in his chair. – His Family by Ernest Poole
  3. He turned to go home, when a sudden thought brought the blood to his face. – Harding's luck by E. [Edith] Nesbit