cruelty

Definition from Nolo’s Plain-English Law Dictionary

Any act of inflicting unnecessary emotional or physical pain. Cruelty or mental cruelty is the most frequently used fault ground for divorce because as a practical matter, courts will accept minor wrongs or disagreements as sufficient evidence of cruelty to justify the divorce. Now that every state has some version of no-fault divorce, cruelty is rarely used as a ground for divorce.

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