Final answer:
Pledging property to a lender as security for a loan, while retaining possession, is called using it as collateral.
Step-by-step explanation:
The act of pledging property to a lender without relinquishing possession rights is known as using the property as collateral for a loan. Collateral is something valuable, often property or equipment, that a lender has a right to take and sell if the borrower fails to repay the loan. In contrast to a cosigner, who is another person or firm that legally pledges to repay the loan if the original borrower does not, offering collateral doesn't necessarily involve another party assuming responsibility for the loan.