stranger has 2 distinct synonyms spread across 1 of its 2 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is acquaintance.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
anyone who does not belong in the environment in which they are found
an individual that one is not acquainted with
Synonyms, antonyms and the broader and narrower relations for stranger come from Princeton University’s WordNet. Full sources and licences.