a legal agreement by which a bank, building society, etc. lends money at interest in exchange for taking title of the debtor's property, with the condition that the conveyance of title becomes void upon the payment of the debt

I put down a hundred thousand in cash and took out a mortgage for the rest

convey (a property) to a creditor as security on a loan

the estate was mortgaged up to the hilt

a heavily mortgaged farm