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

  • n. The act of invading, especially the entrance of an armed force into a territory to conquer.
  • n. A large-scale onset of something injurious or harmful, such as a disease.
  • n. An intrusion or encroachment.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A military action consisting of armed forces of one geopolitical entity entering territory controlled by another such entity, generally with the objective of conquering territory or altering the established government.
  • n. The entry of a large group into a new area.

from the GNU version of the Collaborative International Dictionary of English

  • n. The act of invading; the act of encroaching upon the rights or possessions of another; encroachment; trespass.
  • n. A warlike or hostile entrance into the possessions or domains of another; the incursion of an army for conquest or plunder.
  • n. The incoming or first attack of anything hurtful or pernicious.

from The Century Dictionary and Cyclopedia

  • n. The act of invading a country or territory as an enemy; hostile entrance or intrusion.
  • n. Hence A harmful incursion of any kind; an onset or attack, as of disease.
  • n. Infringement by intrusion; encroachment by entering into or taking away what belongs to another: as, an invasion of one's retirement or rights.
  • n. In phytogeography, the phenomenon of the movement of plants from an area of one character into one of a different character, and their colonization in the latter.

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

  • n. the act of invading; the act of an army that invades for conquest or plunder
  • n. any entry into an area not previously occupied
  • n. (pathology) the spread of pathogenic microorganisms or malignant cells to new sites in the body


Middle English invasioun, from Old French invasion, from Late Latin invāsiō, invāsiōn-, from invāsus, past participle of invādere, to invade; see invade.
(American Heritage® Dictionary of the English Language, Fourth Edition)
From Middle French invasion, from Late Latin invāsiōnem, nominative of invāsiō. (Wiktionary)


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