Intruder

Pronunciation: /ˌɪnˈtruːdər/

Intruder (noun)

  1. A person who enters a place without permission, especially when others do not want them there.
  2. A person who gets involved in a situation where they are not wanted or invited.
  3. In computing, a person or program that enters a system without permission to cause harm or access data.

Examples

  • The guard removed the unwanted visitor from the building.
  • I heard a door open, and I knew an unwanted visitor was inside.