Definition of invasions:
(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 without consent of an individual or group into an area where they are not wanted.
(n) :
(medicine) The spread of cancer cells, bacteria and such to the organism.
(n) :
(surgery) The breaching of the skin barrier.