Impulsive

Part of speech: noun (n.)

That which impels or gives an impulse; an impelling agent. Sir W. Wotton.

Part of speech: adjective (a.)

1. Having the power of driving or impelling; giving an impulse; moving; impellent. Poor men! poor papers! We and they Do some impulsive force obey. Prior.

2. Actuated by impulse or by transient feelings. My heart, impulsive and wayward. Longfellow.

3. Acting momentarily, or by impulse; not continuous; -- said of forces.