Source : Webster's Revised Unabridged Dictionary (1913)

Impulsive \Im*pul"sive\, a. [Cf. F. impulsif.]
   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. (Mech.) Acting momentarily, or by impulse; not continuous;
      -- said of forces.

Impulsive \Im*pul"sive\, n.
   That which impels or gives an impulse; an impelling agent.
   --Sir W. Wotton.

Source : WordNet®

impulsive
     adj 1: proceeding from natural feeling or impulse without external
            stimulus; "an impulsive gesture of affection" [syn: {unprompted}]
     2: without forethought; "letting him borrow her car was an
        impulsive act that she immediately regretted"
     3: having the power of driving or impelling; "a driving
        personal ambition"; "the driving force was his innate
        enthusiasm"; "an impulsive force" [syn: {driving}]
     4: 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" [syn: {capricious}, {whimsical}]
     5: 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) [syn: {hotheaded}, {impetuous}, {madcap},
         {tearaway(a)}, {brainish}]