impulsive

(s) proceeding from natural feeling or impulse without external stimulus
- an impulsive gesture of affection
unprompted,
(s) without forethought
- letting him borrow her car was an impulsive act that she immediately regretted
(s) having the power of driving or impelling
- a driving personal ambition
- the driving force was his innate enthusiasm
- an impulsive force
driving,
(s) determined by chance or impulse or whim rather than by necessity or reason
- a capricious refusal
- authoritarian rulers are frequently capricious
- the victim of whimsical persecutions
whimsical, capricious,
(s) characterized by undue haste and lack of thought or deliberation
- a hotheaded decision
- liable to such impulsive acts as hugging strangers
- an impetuous display of spending and gambling
- madcap escapades; ("brainish" is archaic)
brainish, impetuous, madcap, tearaway, hotheaded,

unprompted driving whimsical capricious brainish impetuous madcap tearaway hotheaded

impulsion

impulsively impulsiveness