A stranger is a person you don't know very well or have never met before.
When you talk about people in everyday life, you might mention the strangers on the bus or at the park. The word "stranger" doesn't necessarily mean someone scary or suspicious - it just means they're not part of your close group of friends or family. You might sit next to a stranger on a plane and strike up a conversation, but often we don't talk to people who are complete strangers because it feels more comfortable to stick with what we know. However, some cities have events where people from all walks of life gather together - like music festivals or street fairs - where you're likely to meet lots of strangers in one place.
How common is "stranger"?
Word stranger is considered uncommon in modern English. It appears most frequently in fiction texts and less often in other writings.
Definitions
adjective
Not normal; odd, unusual, surprising, out of the ordinary.
Example: He thought it strange that his girlfriend wore shorts in the winter.
Unfamiliar, not yet part of one's experience.
Example: I moved to a strange town when I was ten.
Having the quantum mechanical property of strangeness.