Definitionen
1.NounA military action consisting of a large armed force of one geopolitical entity entering territory controlled by another such entity, generally with the objective of conquering territory or altering the established government.
2.NounThe entry without consent of an individual or group into an area where they are not wanted."an invasion of mobile phones; an invasion of bees; an invasion of foreign tourists"
3.NounThe spread of cancer cells, bacteria and such to the organism.
4.NounThe breaching of the skin barrier.