Unpremeditated

Adjective

 * 1) Performed, but not planned or thought out in advance; extemporaneous, but not unintentional.

Antonyms

 * premeditated

Thesaurus
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