Synonym of impulsive

at will ad libitum ad lib without restraint as one thinks best as one wishes according to pleasure

unwary thoughtless impetuous imprudent precipitate spontaneous rash brash reckless hasty irresponsible offhand madcap abrupt instinctive passionate violent ad-lib automatic careless devil-may-care emotional extemporaneous flaky gone off deep end headlong hot-and-cold intuitive involuntary jumping the gun mad quick sudden swift unconsidered unexpected unmeditated unpredictable unpremeditated unprompted up-and-down winging it