Synonyms and related words :
abrupt, alarming, amazing, astonishing, astounding, awesome, awing, breathtaking, chilling, confounding, daunting, deterrent, deterring, disconcerting, discouraging, disheartening, dismaying, disquieting, disturbing, electrifying, eye-opening, fear-inspiring, fearful, fearsome, frightening, frightful, hasty, headlong, impetuous, impulsive, jarring, jolting, mind-boggling, nerve-shattering, overawing, overwhelming, precipitant, precipitate, precipitous, quick, scaring, scary, shocking, spectacular, speedy, staggering, stunning, sudden, surprising, swift, terrifying, unanticipated, unexpected, unforeseen, unlooked-for, unpredicted, unsettling, upsetting