antilapse statute

Under normal estate law, a gift will "lapse" (no longer exist, the gift returns to the will residuary) if the beneficiary predeceases the testator (if the person recieving the gift dies before the person who wrote the will, there is no gift). 

Certain states have enacted "antilapse statutes", under which the gift will pass through the deceased beneficariy and go to their heirs.  For example:  "Grandfather" leaves $100 to his son, "Son", but Son dies before Grandfather.  If there is no antilapse statute, the $100 remains in the estate; but if there is an antilapse statute, the $100 will pass on to Son's heirs, namely "Grandson."