Interloper (noun)

1. A person who becomes involved in a place or situation where they are not wanted or are considered not to belong.
2. A person who intrudes into the affairs of others.
3. An outsider who interferes in the affairs of a group or organization.

Origin:

From middle english entrelouper, entreloper, from old french entrelouper, entreloper, from entre- ("between") + louper ("to jump"), or from inter- + loper ("to jump, leap").

Examples:

1. He felt like an interloper at the party, since he didn't know anyone.
2. She was an interloper in the business, trying to take over the company.
3. He was considered an interloper in the political scene, as he had no prior experience.
4. The interloper was detected and quickly removed from the secured area.
5. The interloper's presence caused tension among the group members.