That which flows or comes in.
A flow inward or into something; a coming in.
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 breaching of the skin barrier.
The spread of cancer cells, bacteries and such to the organism.
The entry without consent of an individual or group into an area where they are not wanted.