unusual person vs someone

unusual person and someone both are nouns.

Word	Noun	Adjective	Verb	Adverb
unusual person	Yes	No	No	No
someone	Yes	No	No	No

As nouns, someone is a hypernym of unusual person; that is, someone is a word with a broader meaning than unusual person:

unusual person: a person who is unusual
someone: a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential

Other hypernyms of unusual person include individual, mortal, person, somebody, soul.

unusual person (noun)	someone (noun)
a person who is unusual	a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential