stranger

A stranger is someone you don't know or who doesn't belong in a specific place.

Parents tell their kids, "Don't talk to strangers." That's because strangers are people they don't know, who could be dangerous. Just like strange things are odd or weird, a stranger is unknown and therefore potentially scary. Also, anyone out of place can be considered a stranger. A fireman in a police station is a stranger, and a mascot in a scientific lab is a stranger. Either type of stranger is likely to make someone say, "Who's that?"

Definitions of stranger
1

n an individual that one is not acquainted with

Antonyms:
acquaintance, friend
a person with whom you are acquainted
Type of:
individual, mortal, person, somebody, someone, soul
a human being

n anyone who does not belong in the environment in which they are found

Synonyms:
alien, unknown
Antonyms:
acquaintance, friend
a person with whom you are acquainted
Types:
foreigner, outsider
someone who is excluded from or is not a member of a group
transalpine
one living on or coming from the other side of the Alps from Italy
Type of:
interloper, intruder, trespasser
someone who intrudes on the privacy or property of another without permission