Dogmatic definition

In Roman Catholicism, a dogmatic definition is an infallible statement published by a pope or an ecumenical council concerning a matter of faith or morals, the belief in which is required of all Christians. Dogmatic definitions by popes are rare. Among them are the definition of Pope Pius XII concerning the Assumption of Mary in 1950 and the definition concerning Mary's Immaculate Conception. [Which pope and which year?]