An intruder is someone who enters a place or situation despite not being invited. If a Girl Scout comes to your door to sell you cookies but ends up trying to watch TV with you, you can call her an intruder.

Some intruders are robbers who break into homes or businesses with the intent to steal things: "The intruder was charged with trespassing, and later was found to have stolen some jewelry and cash." Other intruders might instead invade someone's privacy. Intruder comes from the verb intrude, from the Latin root intrudere, "to thrust in," a combination of in- and trudere, "to thrust or to push."

Definitions of intruder

n someone who intrudes on the privacy or property of another without permission

interloper, 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

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