[n. im-pakt; v. im-pakt]
the striking of one thing against another; forceful contact; collision: The impact of the colliding cars broke the windshield.
an impinging: the impact of light on the eye.
influence; effect: the impact of Einstein on modern physics.
an impacting; forcible impinging: the tremendous impact of the shot.
the force exerted by a new idea, concept, technology, or ideology: the impact of the industrial revolution.
verb (used with object)
to drive or press closely or firmly into something; pack in.
to fill up; congest; throng: A vast crowd impacted St. Peter's Square.
to collide with; strike forcefully: a rocket designed to impact the planet Mars.
to have an impact or effect on; influence; alter: The decision may impact your whole career. The auto industry will be impacted by the new labor agreements.
verb (used without object)
to have impact or make contact forcefully: The ball impacted against the bat with a loud noise.
to have an impact or effect: Increased demand will impact on sales.

1775–85; (noun and v.) back formation from impacted

nonimpact, noun, adjective
postimpact, adjective

The verb impact has developed the transitive sense “to have an impact or effect on” (The structured reading program has done more to impact the elementary schools than any other single factor) and the intransitive sense “to have an impact or effect” (The work done at the computer center will impact on the economy of Illinois and the nation). Although recent, the new uses are entirely standard and most likely to occur in formal speech and writing. See also impactful. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
1.  the act of one body, object, etc, striking another; collision
2.  the force with which one thing hits another or with which two objects collide
3.  the impression made by an idea, cultural movement, social group, etc: the impact of the Renaissance on Medieval Europe
4.  to drive or press (an object) firmly into (another object, thing, etc) or (of two objects) to be driven or pressed firmly together
5.  to have an impact or strong effect (on)
[C18: from Latin impactus pushed against, fastened on, from impingere to thrust at, from pangere to drive in]

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
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Word Origin & History

c.1600, "press closely into something," from L. impactus, pp. of impingere "to push into, dash against" (see impinge). Originally sense preserved in impacted teeth (1876). Sense of "strike forcefully against something" first recorded 1916. Figurative sense began with use
as a noun (1817, first in Coleridge) meaning "effect of coming into contact with a thing or person."
Online Etymology Dictionary, © 2010 Douglas Harper
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Encyclopedia Britannica


in physics, the sudden, forceful coming together in direct contact of two bodies, such as, for example, two billiard balls, a golf club and a ball, a hammer and a nail head, two railroad cars when being coupled together, or a falling object and a floor. Apart from the properties of the materials of the two objects, two factors affect the result of impact: the force and the time during which the objects are in contact. It is a matter of common experience that a hard steel ball dropped on a steel plate will rebound to almost the position from which it was dropped, whereas with a ball of putty or lead there is no rebound. The impact between the steel ball and plate is said to be elastic, and that between the putty or lead balls and plate is inelastic, or plastic; between these extremes there are varying degrees of elasticity and corresponding responses to impact. In a perfectly elastic impact (attained only at the atomic level), none of the kinetic energy of the coacting bodies is lost; in a perfectly plastic impact, the loss of kinetic energy is at a maximum.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
These products reduce the impact of logging by blending plastic with wood fiber.
None of these species are listed as endangered, but no one knows the potential
  impact from thousands of deaths each year.
These far-reaching effects illustrate the profound impact air pollution can
  have on the land.
It is not clear whether there is any such thing as global warming and what if
  any its impact is on this region.
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