Intrusion \In*tru"sion\, n. [Cf. F. intrusion. See Intrude.]

1. The act of intruding, or of forcing in; especially, the forcing (one's self) into a place without right or welcome; encroachment.

Why this intrusion? Were not my orders that I should be private? --Addison.

2. (Geol.) The penetrating of one rock, while in a plastic or metal state, into the cavities of another.

3. (Law) The entry of a stranger, after a particular estate or freehold is determined, before the person who holds in remainder or reversion has taken possession.

4. (Scotch Ch.) The settlement of a minister over 3 congregation without their consent.

Source: Webster's Revised Unabridged Dictionary (1913)