intruder

/ɪnˈtruːdər/
noun
  1. A person who enters a place without permission, especially with the intent to commit a crime.
    • We heard a noise downstairs and feared an intruder was in the house.
    • The security system alerted the police when an intruder entered the building.
    • The garden gate was locked to keep out any intruders.
  2. Someone who becomes involved in a situation where they are not wanted or welcome.
    • She tried not to be an intruder in their private discussion.
    • At the family gathering, the new boyfriend felt like an intruder.
    • The journalist was seen as an intruder in the closed community meeting.
Antonyms
What does "intruder" mean? | whatsthatwordmean | whatsthatwordmean