impulsive

[1]

impetuous , emotional , unpredictable , unpremeditated , unplanned , spur-of-the-moment , extemporaneous , unconsidered , offhand , instinctive , involuntary , spontaneous , quick , sudden , precipitate , immediate , snap , rash , headlong , rash , reckless , devil-may-care , foolhardy , madcap , wild

adj.

[1]	unprompted
[2]	driving
[3]	capricious , whimsical
[4]	hotheaded , impetuous , madcap , tearaway , brainish