define a grantor trust
From Wikipedia, the free encyclopedia. A grantor retained annuity trust (commonly referred to by the acronym GRAT), is a financial instrument commonly used in the United States to make large financial gifts to family members without paying a U.S. gift tax.rom Wikipedia, the free encyclopedia. A grantor retained annuity trust (commonly referred to by the acronym GRAT), is a financial instrument commonly used in the United States to make large financial gifts to family members without paying a U.S. gift tax.