INVASION
invasion
(noun) the act of invading; the act of an army that invades for conquest or plunder
invasion
(noun) (pathology) the spread of pathogenic microorganisms or malignant cells to new sites in the body; “the tumor’s invasion of surrounding structures”
invasion, encroachment, intrusion
(noun) any entry into an area not previously occupied; “an invasion of tourists”; “an invasion of locusts”
Source: WordNet® 3.1
Etymology
Noun
invasion (countable and uncountable, plural invasions)
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.
The entry without consent of an individual or group into an area where they are not wanted.
(medicine) The spread of cancer cells, bacteries and such to the organism.
(surgery) The breaching of the skin barrier.
Source: Wiktionary
In*va"sion, n. Etym: [L. invasio: cf. F. invasion. See Invade.]
1. The act of invading; the act of encroaching upon the rights or
possessions of another; encroachment; trespass.
2. A warlike or hostile entrance into the possessions or domains of
another; the incursion of an army for conquest or plunder.
3. The incoming or first attack of anything hurtful or pernicious;
as, the invasion of a disease.
Syn.
– Invasion, Irruption, Inroad. Invasion is the generic term,
denoting a forcible entrance into a foreign country. Incursion
signifies a hasty and sudden invasion. Irruption denotes particularly
violent invasion. Inroad is entry by some unusual way involving
trespass and injury.
Source: Webster’s Unabridged Dictionary 1913 Edition