a stranger to something Definition

1. Someone that one does not know.

Example: a perfect stranger
Example: a total stranger
2. Someone who comes from a different place, home town, family, etc.

Thesaurus: foreigner, outsider, newcomer, intruder, visitor, alien, guest, immigrant; Antonym: inhabitant, citizen, native.

Someone who is unfamiliar with or inexperienced in something.
Example: He's no stranger to trouble