Synonyms and related words :
ad-lib, aimless, caught napping, caught off balance, caught short, designless, desultory, extemporaneous, extemporized, haphazard, hasty, hit-or-miss, impromptu, improvised, inadvertent, indiscriminate, involuntary, makeshift, precipitate, purposeless, rough-and-ready, snap, surprised, taken aback, taken by surprise, taken unawares, tripped up, unarranged, unbegun, unconcocted, unconscious, unconsidered, uncontrived, undeliberated, undesigned, undevised, unguarded, unguided, unhatched, unintended, unintentional, unmade, unmanufactured, unmeant, unmeditated, unorganized, unpremeditated, unprepared, unprimed, unprompted, unpurposed, unready, unstudied, unthinking, unthought, unthought-of, unwitting