1. The act of impelling, or driving onward with sudden force; impulsion; especially, force so communicated as to produced motion suddenly, or immediately. "All spontaneous animal motion is performed by mechanical impulse." (S. Clarke)

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

3. <mechanics> 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.

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. "These were my natural impulses for the undertaking." (Dryden)

Synonyms: Force, incentive, influence, motive, feeling, incitement, instigation.

Origin: L. Impulsus, fr. Impellere. See Impel.

(01 Mar 1998)