| spontaneous(noun, adjective, passionate, violent, careless) |
| steep(adjective, sharp, sheer, vertical) |
| suddenly(adverb, unexpectedly, unawares, abruptly, ignorantly) |
| unexpectedly(adverb, short, suddenly, unawares, abruptly) |
| extraordinary(wonderful, shocking, astonishing, astounding) |
| eye-opening(adjective, amazing, astonishing, astounding, dumbfounding) |
| impromptu(adjective, impulse, unexpected, quickly) |
| lightning |
| out of the blue(expression, adjective, idiom, wonderful, abrupt) |
| overhasty(impulsive, reckless, hasty, irascibility) |
| rushing(adjective, violent, fierce, quick, ardent) |
| unpredictable(noun, extraordinary, passionate, violent, wonderful) |
| without warning(expression, adjective, adverb, wonderful, suddenly) |
| aback(short, suddenly, unexpectedly, unawares, abruptly) |
| absolute |
| all at once(expression, idiom) |
| astonishing(adjective, extraordinary, wonderful, shocking, astounding) |
| breakneck(adjective, keen, sharp, energetic, active) |
| brief(fast, quick, speedy, swift, immediate) |
| curt(adjective, keen, energetic, violent, active) |