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Webster 1913 Edition
Frank-marriage
Frank′-mar′riage
,Noun.
 [
Frank 
free + marriage
.] (Eng. Law) 
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. 
[Obs.] 
Blackstone.
 Definition 2025
frank-marriage
frank-marriage
English
Noun
frank-marriage (plural frank-marriages)
-  (obsolete, Britain, law) A kind of estate tail.
- (Can we find and add a quotation of Blackstone to this entry?)