Copied from a probate site - hope it helps
The word is “lapse.” If a Testator gives something to someone (the beneficiary) in his will, what happens if the beneficiary dies before the Testator?
The general rule is that if the beneficiary is a descendant of the Testator, i.e. his children or grand children, the gift goes to the beneficiary’s descendants. The same would be true if the beneficiary is a descendant of the Testator‘s parents.
If the beneficiary is not a descendant of the Testator or of the Testator‘s parents, the gift lapses and goes to the person named as the residuary beneficiary. The residuary beneficiary is the person who the Testator names as the person who gets “all the rest and residue of my estate.”
If the residuary beneficiary dies before the Testator and is not a descendant of the Testator or of the Testator‘s parents, the gift lapses and the Testator dies intestate as to the property that would be in the residuary estate. It would then go to the Testator‘s heirs at law.