frank-marriage

from The Century Dictionary.

• noun In old Eng, law, an estate of inheritance given to a man together with his wife (being a daughter or near relative of the donor), and descendible to the heirs of their two bodies begotten, to be held free of service other than fealty, to the fourth generation.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Eng. Law), obsolete A certain tenure in tail special; an estate of inheritance given to a man his wife (the wife being of the blood of the donor), and descendible to the heirs of their two bodies begotten.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun obsolete, UK, law A kind of estate tail.