The Collaborative International Dictionary of English v.0.48:

Impulse \Im*pulse"\, v. t. [See Impel.]
   To impel; to incite. [Obs.] --Pope.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Impulse \Im"pulse\, n. [L. impulsus, fr. impellere. See
   Impel.]
   [1913 Webster]
   1. The act of impelling, or driving onward with sudden force;
      impulsion; especially, force so communicated as to
      produced motion suddenly, or immediately.
      [1913 Webster]

            All spontaneous animal motion is performed by
            mechanical impulse.                   --S. Clarke.
      [1913 Webster]

   2. The effect of an impelling force; motion produced by a
      sudden or momentary force.
      [1913 Webster]

   3. (Mech.) The action of a force during a very small interval
      of time; the effect of such action; as, the impulse of a
      sudden blow upon a hard elastic body.
      [1913 Webster]

   4. A mental force which simply and directly urges to action;
      hasty inclination; sudden motive; momentary or transient
      influence of appetite or passion; propension; incitement;
      as, a man of good impulses; passion often gives a violent
      impulse to the will; to buy something on impulse.
      [1913 Webster +PJC]

            These were my natural impulses for the undertaking.
                                                  --Dryden.

   Syn: Force; incentive; influence; motive; feeling;
        incitement; instigation.
        [1913 Webster]

WordNet (r) 3.0 (2006):

impulse
    n 1: an instinctive motive; "profound religious impulses" [syn:
         urge, impulse]
    2: a sudden desire; "he bought it on an impulse" [syn:
       caprice, impulse, whim]
    3: the electrical discharge that travels along a nerve fiber;
       "they demonstrated the transmission of impulses from the
       cortex to the hypothalamus" [syn: nerve impulse, nervous
       impulse, neural impulse, impulse]
    4: (electronics) a sharp transient wave in the normal electrical
       state (or a series of such transients); "the pulsations
       seemed to be coming from a star" [syn: pulsation,
       pulsing, pulse, impulse]
    5: the act of applying force suddenly; "the impulse knocked him
       over" [syn: impulse, impulsion, impetus]
    6: an impelling force or strength; "the car's momentum carried
       it off the road" [syn: momentum, impulse]

Moby Thesaurus II by Grady Ward, 1.0:

81 Moby Thesaurus words for "impulse":
   actuation, archetypal pattern, archetype, atomic power,
   automatic writing, automatism, blind impulse, catalyst,
   collective unconscious, compulsion, compulsiveness, conditioning,
   constraint, drive, echolalia, echopraxia, electric power,
   electropower, excitant, exigency, forwardness, goad, haste,
   hastiness, horsepower, hydraulic power, hydroelectric power, id,
   impetus, impulsion, impulsiveness, inborn proclivity, incentive,
   incitation, incitement, instinct, instinctiveness, involuntariness,
   jet power, libido, lust, manpower, motivation, natural instinct,
   natural tendency, nuclear power, overhastiness, passion, pinch,
   piston power, precipitation, precociousness, precocity,
   prematureness, prematurity, press, pressure, primitive self,
   propulsion, push, rash impulse, reflex action, rocket power, rush,
   sheer chemistry, solar power, spur, steam power, stimulant, stress,
   subconscious urge, thermonuclear power, thrust, unlearned capacity,
   unreasoning impulse, untimeliness, unwilledness, urge, urgency,
   vital impulse, water power