المعنى الاصطلاحي :

Violating one's oath by doing what one swore not to do or by leaving what one swore to do.

الشرح المختصر :

"Hinth" (violation of an oath): Any oath has three stages: a beginning, which is taking an oath; an end, which is expiation; and a middle, which is "hinth", i.e. doing what one took an oath to leave or leaving what one took an oath to do. According to this, "hinth" is not applicable to any oath taken upon something in the past, and so there is no penalty of expiation. Saying the truth, however, is a fulfillment of one's oath; otherwise "hinth" is a sin. As for expiation, it is applicable to oaths taken for future matters only.

التعريف اللغوي المختصر :

"Hinth": major sin, wrongdoing. Opposite: "birr" (fulfillment of oath). Other meanings: breaking an oath.