impulse

[im-puhls]
noun
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.
adjective
10.
marked by or acting on impulse: an impulse buyer.
11.
bought or acquired on impulse: To reduce expenses, shun impulse items when shopping.

Origin:
1640–50; < Latin impulsus pressure, impulse, equivalent to im- im-1 + pul- (variant stem of pellere to push) + -sus, variant of -tus suffix of v. action

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World English Dictionary
impulse (ˈɪmpʌls)
 
n
1.  an impelling force or motion; thrust; impetus
2.  a sudden desire, whim, or inclination: I bought it on an impulse
3.  an instinctive drive; urge
4.  tendency; current; trend
5.  physics
 a.  the product of the average magnitude of a force acting on a body and the time for which it acts
 b.  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
8.  on impulse spontaneously or impulsively
 
[C17: from Latin impulsus a pushing against, incitement, from impellere to strike against; see impel]

Collins English Dictionary - Complete & Unabridged 10th Edition
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Etymonline
Word Origin & History

impulse
early 15c., "an act of impelling, a thrust, push," from L. impulsus "a push against, pressure, shock," also "incitement, instigation," pp. of impellere (see impel). Meaning "stimulus in the mind arising from some state or feeling" first recorded 1640s.
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

impulse im·pulse (ĭm'pŭls')
n.

  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.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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American Heritage
Science Dictionary
impulse   (ĭm'pŭls')  Pronunciation Key 
  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.


The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Example sentences
It was never intended as homage to him, but really to that period of my life,
  which was really the first impulse of this movie.
One afternoon at the river camp three settlers appeared in a dugout canoe,
  drawn by the universal impulse to gawk at disaster.
My legs twitched involuntarily, the movement an outward manifestation of an
  impulse to flee.
On impulse, you grab an extra-large candy bar during your afternoon break.
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