As others said, it depends who you ask. The Augustinian view was that usury isn't defined by the rate but when, and I'm explaining this rather poorly, interest is charged for the use of money. Hence "usury." So a typical American mortgage would be usurious in the Augustinian definition, even if the interest rate were, say, 1%.
The alternative non-usurious loan would require you to post some other kind of security to receive the money, such as giving the lender the use of some other productive land until the principal debt is paid. More like pawning something at a pawn shop and then buying it back when you get paid.