It stands for gross weighted average coupon; the actual weighted- average coupon (WAC) of a pool of mortgages that backs a security. Gross WAC reflects the investor’s proceeds from a mortgage pass-through (PT) that is stated on a gross basis (i.e., before deducting any servicing fee that is paid for the loan. Servicing fees (servicing spread charged by the originating lender) may include the mortgage interest payment, property taxes, mortgage insurance premium, property insurance.

Gross WAC is equal to net WAC plus servicing spread.