/ ɪnˈveɪʒn; NAmE / noun [ C , U ]
1.
the act of an army entering another country by force in order to take control of it :
the Russian invasion of Czechoslovakia in 1968
the threat of invasion
an invasion force / fleet
2.
the fact of a large number of people or things arriving somewhere, especially people or things that are disturbing or unpleasant :
the annual tourist invasion
Farmers are struggling to cope with an invasion of slugs.
3.
an act or a process that affects sb/sth in a way that is not welcome :
The actress described the photographs of her as an invasion of privacy .
—see also invade
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WORD ORIGIN
late Middle English : from late Latin invasio(n-) , from the verb invadere , from in- into + vadere go.