Impulsive

1. n. That which impels or gives an impulse; an impelling agent.
2. a. Having the power of driving or impelling; giving an impulse; moving; impellent.
3. a. Actuated by impulse or by transient feelings.
4. a. Acting momentarily, or by impulse; not continuous; — said of forces.

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.