from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun The striking of one body against another; collision. synonym: collision.
  • noun The force transmitted by a collision.
  • noun The effect or impression of one person or thing on another.
  • intransitive verb To pack firmly together.
  • intransitive verb To strike forcefully.
  • intransitive verb Usage Problem To have an effect or impact on.
  • intransitive verb To have an effect or impact.

from The Century Dictionary.

  • To drive close; press closely or firmly; pack in.
  • noun The act of striking against something; a blow; a stroke.
  • noun Specifically — In mech., the blow, or act of striking, of a body having momentum; also, the change of momentum in amount and direction produced by such a blow.
  • noun In gunnery, the single blow of a projectile against a fixed or moving object.

from the GNU version of the Collaborative International Dictionary of English.

  • noun Contact or impression by touch; collision; forcible contact; force communicated.
  • noun (Mech.) The single instantaneous stroke of a body in motion against another either in motion or at rest.
  • transitive verb To drive close; to press firmly together: to wedge into a place.
  • transitive verb To affect or influence, especially in a significant or undesirable manner.
  • transitive verb To collide forcefully with; to strike.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun The force or energy of a collision of two objects.
  • noun A forced impinging.
  • noun A significant or strong influence; an effect.
  • verb transitive To compress; to compact; to press or pack together.
  • verb transitive, proscribed To influence; to affect; to have an impact on.
  • verb transitive To collide or strike.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • verb press or wedge together; pack together
  • noun a forceful consequence; a strong effect
  • noun influencing strongly
  • verb have an effect upon
  • noun the striking of one body against another
  • noun the violent interaction of individuals or groups entering into combat


from The American Heritage® Dictionary of the English Language, 4th Edition

[From Latin impāctus, past participle of impingere, to push against; see impinge.]

from Wiktionary, Creative Commons Attribution/Share-Alike License

From Latin impāctus, perfect passive participle of impingō ("dash against, impinge").


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  • This word is used (and misused) in business speak: "that new product will have a big impact on our sales." Or worse: "the change to our commercial will be impactful on our third-quarter sales." Every time I hear the word used this way, I think about impaction of the bowel, and I see that Ninjawords uses that as an example in its definition of the word.

    December 12, 2006

  • What's the impact this word?

    October 9, 2008

  • Impact as a verb is unpleasant, brutal, painful. I cringe. My skin crawls.

    May 8, 2009

  • I know it's a losing battle by now, but I will never abide this word as a transitive verb. You don't "impact" something, you "affect" it. You can destroy it, tame it, lengthen it, shorten it, kill it, nurture it, hurt it, help it, bend it, build it, or do any number of other things to affect it, but you don't "impact" it!

    June 10, 2009

  • Using this as both a noun meaning "effect" and verb meaning "affect" avoids the confusion between these two similar words. Maybe this is why it's so popular.

    June 27, 2009

  • GlamourGirl, I agree!

    November 16, 2009

  • I've never had a problem differentiating between "affect" and "effect." They are spelled differently and pronounced differently (however slight that difference may seem). Impact as a verb is used primarily by the moderately educated and the pretentious, such as weather forecasters who say things like: "The liquid precipitation will impact your commute tomorrow morning," when they should just tell us that it's going to rain.

    January 1, 2012

  • "In any given perception there is something which has been communicated to it by an impact, or an impression." -Biographia Literaria, 1817

    The word had been used to describe a physical collision since the 1600s, but Coleridge was the first to use it in a metaphorical sense.

    March 5, 2018