stranger vs outsider

stranger and outsider both are nouns.

Word	Noun	Adjective	Verb	Adverb
stranger	Yes	No	No	No
outsider	Yes	No	No	No

As nouns, outsider is a hyponym of stranger; that is, outsider is a word with a more specific, narrower meaning than stranger:

stranger: anyone who does not belong in the environment in which they are found
outsider: someone who is excluded from or is not a member of a group

Other hyponyms of stranger include foreigner.

stranger (noun)	outsider (noun)
anyone who does not belong in the environment in which they are found	someone who is excluded from or is not a member of a group
an individual that one is not acquainted with	a contestant (human or animal) not considered to have a good chance to win