n. [ F. trisaïeul, from L. tris, tres, three + F. aïeul grandfather. Cf. Besaiel, and see Ayle. ] A grandfather's grandfather. [ Obs. ] [ 1913 Webster ]

Writ of tresayle (O. Eng. Law), a writ which lay for a man claiming as heir to his grandfather's grandfather, to recover lands of which he had been deprived by an abatement happening on the ancestor's death. Mozley & W. [ 1913 Webster ]