Defined Terms and Documents       

Usury is the practice of making unethical or immoral monetary loans that unfairly enrich the lender, or in laymen's term, lending at an unreasonably high rate of interest.  A loan may be considered Usurious because of excessive or abusive interest rates or other factors.

See:

Usurious Unsecured Personal Loan Interest Rates Charged On Many Credit Cards

Study on interest rate restrictions in the EU