1. The legal or customary right of inheritance or succession by the firstborn son of a family: Because he and his wife only had daughters, Lord Seymore was puzzled about the custom of primogeniture in terms of the family estate.
2. The patrilineal mode of succession by which the right of inheritance pertains to the firstborn son of a family, to the exclusion of females: In older times, the lord of an estate might legally adopt a male child in order to preserve the custom of primogeniture when determining the terms of his will with respect to the inheritance of his property.
3. Etymology: from Latin, “firstborn”; from primus, “first” + genitura, “birth”.