Synonyms and related words :
a bit previous, ad lib, ad-lib, advanced, automatic, casual, caught napping, caught off balance, caught short, coincidental, extemporaneous, extemporary, extempore, extemporized, far ahead, forward, gut, half-baked, half-cocked, haphazard, hasty, ill-advised, ill-considered, ill-devised, impromptu, improvised, impulsive, inadvertent, indeliberate, involuntary, last-minute, makeshift, natural, not firm, off the cuff, offhand, overhasty, oversoon, precipitate, precocious, premature, previous, reflex, reflexive, rough-and-ready, rushed, snap, spontaneous, spur-of-the-moment, surprised, taken aback, taken by surprise, taken unawares, too early, too soon, tripped up, unadvised, unarranged, unbegun, uncalculated, unconcocted, unconscious, unconsidered, uncontrived, uncrystallized, undeliberate, undeliberated, undesigned, undevised, unguarded, unguided, unhatched, unintended, unintentional, unjelled, unmade, unmanufactured, unmatured, unmeant, unmeditated, unorganized, unplanned, unprepared, unprimed, unprompted, unpurposed, unready, unripe, unstudied, unthinking, unthought, unthought-of, untimely, unwilled, unwitting