A security that "passes through" monthly the interest and principal cash flows from a pool of underlying mortgage loans.
The servicer of a pool of mortgages collects the borrower’s monthly payments and, after deducting a fee, remits or passes them through to the security holders or investors. The pas-through is the most common structure for mortgage-backed securities.
A bond, certificate, or other form of security collateralized by a block of mortgage loans. Monthly payments on the mortgage loans are "passed through" a trustee to the holder of the securities.