aback, abruptly, accidentally, bang, by accident, by surprise, dash, guiltlessly, hastily, ignorantly, impetuously, implausibly, improbably, impulsively, inadvertently, innocently, insensibly, like a flash, like a thunderbolt, mistakenly, of a sudden, off base, on short notice, plop, plump, plunk, pop, precipitantly, precipitately, precipitously, sharp, short, slap, smack, startlingly, sudden, suddenly, surprisingly, unanticipatedly, unaware, unconsciously, unexpectedly, unforeseeably, unguiltily, unintentionally, unknowingly, unmindfully, unpredictably, unprepared, unready, unsuspectingly, unwittingly, without notice, without warning, witlessly