If you intrude on people without their permission, you are an interloper. An interloper crashes parties and laughs at "No Trespassing" signs.

Interloper was likely formed by combining inter-, ("between") with -loper, (from landloper, meaning "vagabond" or "adventurer"). An interloper, then, is someone who has ventured or traveled where he was not welcome. The noun interloper may also refer to something other than a person: "The new chain superstore built at the edge of town and was an interloper among the various mom-and-pop grocery stores in the area."

Definitions of interloper
  1. noun
    someone who intrudes on the privacy or property of another without permission
    synonyms: intruder, trespasser
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    someone who forces their way aboard ship
    crasher, gatecrasher, unwelcome guest
    someone who gets in (to a party) without an invitation or without paying
    an intruder (as troops) with hostile intent
    encroacher, invader
    someone who enters by force in order to conquer
    an intruder who passes into or through (often by overcoming resistance)
    prowler, sneak, stalker
    someone who prowls or sneaks about; usually with unlawful intentions
    pusher, thruster
    one who intrudes or pushes himself forward
    someone who settles on land without right or title
    alien, stranger, unknown
    anyone who does not belong in the environment in which they are found
    foreigner, outsider
    someone who is excluded from or is not a member of a group
    type of:
    persona non grata, unwelcome person
    a person who for some reason is not wanted or welcome
    someone who enters
Word Family

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