1. the influence of a particular feeling, mental state, etc.: to act under a generous impulse; to strike out at someone from an angry impulse.
  2. sudden, involuntary inclination prompting to action: to be swayed by impulse.
  3. an instance of this.
  4. a psychic drive or instinctual urge.
  5. an impelling action or force, driving onward or inducing motion.
  6. the effect of an impelling force; motion induced; impetus given.
  7. Physiology. a progressive wave of excitation over a nerve or muscle fiber, having either a stimulating or inhibitory effect.
  8. Mechanics. the product of the average force acting upon a body and the time during which it acts, equivalent to the change in the momentum of the body produced by such a force.
  9. Electricity. a single, usually sudden, flow of current in one direction.


  1. marked by or acting on impulse: an impulse buyer.
  2. bought or acquired on impulse: To reduce expenses, shun impulse items when shopping.


  1. an impelling force or motion; thrust; impetus
  2. a sudden desire, whim, or inclinationI bought it on an impulse
  3. an instinctive drive; urge
  4. tendency; current; trend
  5. physics
    1. the product of the average magnitude of a force acting on a body and the time for which it acts
    2. the change in the momentum of a body as a result of a force acting upon it for a short period of time
  6. physiol See nerve impulse
  7. electronics a less common word for pulse 1 (def. 2)
  8. on impulse spontaneously or impulsively

early 15c., “an act of impelling, a thrust, push,” from Latin impulsus “a push against, pressure, shock,” also “incitement, instigation, impulse,” past participle of impellere (see impel). Meaning “stimulus in the mind arising from some state or feeling” first recorded 1640s.


  1. A sudden pushing or driving force.
  2. A sudden wish or urge that prompts an unpremeditated act or feeling; an abrupt inclination.
  3. The electrochemical transmission of a signal along a nerve fiber that produces an excitatory or inhibitory response at a target tissue.

  1. A sudden flow of electrical current in one direction.
  2. An electrical signal traveling along the axon of a neuron. Nerve impulses excite or inhibit activity in other neurons or in the tissues of the body, such as muscles and glands.
  3. The change of momentum of a body or physical system over a time interval in classical mechanics, equal to the force applied times the length of the time interval over which it is applied.
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