Intrusion

Noun

1. The forcible inclusion or entry of an external group or individual; the act of intruding.

   "She viewed sales calls as an unwelcome intrusion."

2. Magma forced into other rock formations; the rock formed when such magma solidifies.
3. A structure that lies within a historic district but is nonhistoric and irrelevant to the district.
4. The insertion of a phoneme into the pronunciation of a word despite its absence from the spelling. (e.g. intrusive r)
5. An involuntarily arising idea or memory that is nuisant and falsifies an accurate impression of the world.