Stranger

Person who is unknown to other persons

A stranger is a person who is unknown or unfamiliar to another person or group. Because of this unknown status or unfamiliarity, a stranger may be perceived as a threat until their identity and character can be ascertained. Different classes of strangers have been identified for social science purposes, and the tendency for strangers and foreigners to overlap has been examined.

From Wikipedia, under CC BY-SA. More on occurri.