octoroon vs mixed-blood

octoroon and mixed-blood both are nouns.

Word	Noun	Adjective	Verb	Adverb
octoroon	Yes	No	No	No
mixed-blood	Yes	No	No	No

As nouns, mixed-blood is a hypernym of octoroon; that is, mixed-blood is a word with a broader meaning than octoroon:

octoroon: an offspring of a quadroon and a white parent; a person who is one-eighth black
mixed-blood: a person whose ancestors belonged to two or more racial groups

octoroon (noun)	mixed-blood (noun)
an offspring of a quadroon and a white parent; a person who is one-eighth black	a person whose ancestors belonged to two or more racial groups