interloper

UK: /ˈɪntə^rləʊpə^r/ US: /ˈɪntɚˌloʊpɚ/

WordReference Random House Learner's Dictionary of American English © 2025

in•ter•lop•er /ˈɪntɚˌloʊpɚ/   n. [countable]

1. a person who intrudes on the field of interest or business of others.

Collins Concise English Dictionary © HarperCollins Publishers::

interloper / ˈɪntəˌləʊpə/ noun

1. an intruder
2. a person who gains entry into professional or social circles where he or she does not belong
3. a person who interferes in matters that are not his or her concern

Etymology: 17th Century: from inter- + loper, from Middle Dutch loopen to leap

WordReference Random House Unabridged Dictionary of American English © 2025

in•ter•lope  (in′tər lōp′, in′tər lōp′), v.i., -loped, -lop•ing. 

1. to intrude into some region or field of trade without a proper license.
2. to thrust oneself into the affairs of others.

• probably back formation from interloper, equivalent. to inter- + -loper (see landloper) 1595–1605

in′ter•lop′er, n. 
Synonyms

• 1. trespass, poach, encroach.
• 2. meddle.