extreme cruelty

Definition from Nolo’s Plain-English Law Dictionary

A ground for divorce based on the infliction of physical or mental harm on one spouse by the other. Although all states now have "no-fault divorce," some states still recognize fault as a ground for divorce, and in other states evidence of cruelty may result in division of property that favoring who was the victim of extreme cruelty.

Definition provided by Nolo’s Plain-English Law Dictionary.