What term refers to the act of lending money at an exorbitant rate of interest?

The term that refers to the act of lending money at an exorbitant rate of interest is "usury." Usury has its origins in historical legal systems where it denoted the practice of charging excessively high-interest rates on loans, which was often considered exploitative and had moral and ethical implications. This term is specific in identifying the problem of lending practices that take advantage of individuals or businesses in dire financial circumstances.

The other options do not relate to the act of lending money at high interest. For instance, "tyro" refers to a beginner or novice in a particular field, "upbraid" means to scold or criticize, and "turpitude" refers to depravity or moral corruption. None of these terms encompass the idea of exploitative lending practices, making "usury" the precise and accurate choice in this context.