interloper

/ˈɪntərˌloʊpər/

Other forms: interlopers

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

   types:

   boarder

   someone who forces their way aboard ship

   crasher, gatecrasher, unwelcome guest

   someone who gets in (to a party) without an invitation or without paying

   infiltrator

   an intruder (as troops) with hostile intent

   encroacher, invader

   someone who enters by force in order to conquer

   penetrator

   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

   squatter

   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

   entrant

   someone who enters