A mortgage that has a first-priority claim against the property in the event the borrower defaults on the loan. For example, a borrower defaults on a loan secured by a property worth $100,000 net of sale costs. The property has a first mortgage with a balance of $90,000 and a second mortgage with a balance of $15,000. The first mortgage lender can collect $90,000 plus any unpaid interest and foreclosure costs. The second mortgage lender can collect only what is left of the $100,000.