KJV Dictionary Definition: birthright
BIRTH'RIGHT, n. birth and right. Any right or privilege, to which a person is entitled by birth, such as an estate descendible by law to an heir, or civil liberty under a free constitution.
Esau, for a morsel, sold his birthright. Heb.12.
It may be used in the sense of primogeniture,or the privilege of the first born, but is applicable to any right which results from descent.