What is Quadroon?

Legal Definition
Historically in the context of slave societies of the Americas, a quadroon or quarteron was a mixed-race person with one quarter African and three quarters European ancestry (or in the context of Australia, one quarter aboriginal ancestry).

Similar classifications were octoroon for one eighth black and hexadecaroon for one sixteenth black.

Governments incorporated the terms in law defining rights and restrictions. The use of such terminology is a characteristic of hypodescent, which is the practice within a society of assigning children of mixed unions to the ethnic group which is perceived by the dominant group as being subordinate. The racial designations refer specifically to the number of full-blooded African ancestors or equivalent, emphasizing the quantitative least, with quadroon signifying that a person has one-quarter black ancestry.
-- Wikipedia
Legal Definition
A person who is descended from a white person, and another person who has an equal mixture of the European and African blood. 2 Bailey, 558. Vide Mulatto.
-- Bouviers Law Dictionary
Legal Definition
A person who is descended from a white person and another person who has an equal mixture of the European and African blood. State v. Davis, 2 Bailey (S. Ct) 558.
-- Black's Law Dictionary
Legal Definition
One distinctly whiter than a mulatto. See 126 La. 300, 139 Am. St. Rep. 514, 20 Ann. Cas. 1297, 52 South. 500; the issue of a white person and one half black.
-- Ballentine's Law Dictionary