The striking of one body against another; collision. See Synonyms at collision. The force or impetus transmitted by a collision. The effect or impression of one thing on another: still gauging the impact of automation on the lives of factory workers. The power of making a strong, immediate impression: a speech that lacked impact. To pack firmly together. To strike forcefully: meteorites impacting the lunar surface. Usage Problem To have an effect or impact on: "No region ... has been more impacted by emerging demographic and economic trends\u201d ( Joel Kotkin). Usage Problem To have an effect or impact.