Noun. ‘ˈmæntrə’ a commonly repeated word or phrase. Noun, singular or mass The teacher may begin or mantra synonym end practice with a mantra. ‘ˈmæntrə’ a commonly repeated word or phrase. Noun, singular or mass The teacher may begin or end practice with a mantra. Noun. ‘ˈmæntrə’ a commonly repeated word or phrase. Noun.