1. (a.) Happening without previous notice or with very brief notice; coming unexpectedly, or without the common preparation; immediate; instant; speedy.

2. (a.) Hastily prepared or employed; quick; rapid.

3. (a.) Hasty; violent; rash; precipitate.

4. (adv.) Suddenly; unexpectedly.

5. (n.) An unexpected occurrence; a surprise.

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