intrusion

noun intrusions

1. countable, uncountable The forcible inclusion or entry of an external group or individual; the act of intruding. She viewed sales calls as an unwelcome intrusion.
2. countable, uncountable A penetration by hackers, a computer virus, etc. The intrusion of the virus rendered our other security efforts useless.
3. countable, uncountable The insertion of a phoneme into the pronunciation of a word despite its absence from the spelling. (e.g. intrusive r) A current challenge in recent work on Spanish sound structure is to understand the conditions that determine vowel intrusion and the consequences vowel intrusion may have on Spanish phonology.
4. uncountable A feeling of being intruded upon; the state or condition of being intruded. I watched and felt intrusion upon the reigning terror of them
5. countable, uncountable Magma forced into other rock formations; the rock formed when such magma solidifies.
6. countable, uncountable A structure that lies within a historic district but is nonhistoric and irrelevant to the district. This setting is slightly altered by modern intrusion.
7. countable, uncountable An involuntarily arising idea or memory that is nuisant and falsifies an accurate impression of the world. In general, intrusion errors tend to occur with greater frequency in individuals whose cognitive capacity is diminished relative to that of young adults. Poor readers, older participants, and neuropsychological patients exhibit more intrusion errors than controls.
8. collective, countable, rare, uncountable A swarm or nest of cockroaches, infesting a structure. When I turned on the light, scattered mats of cockroach intrusions scurried into the walls.