Sub Stitution
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
In the civil law. The putting one person in place of another; particularly, the act of a testator in naming a second devisee or legatee who is to take the bequest either on failure of the original devisee or legatee or after him.
In Scotch law
The enumeration or designation of the heirs in a settlement of property. Substitutes in an entail are those heirs who are appointed in succession on failure of others.