menses Syllabification: (men·ses)Pronunciation: /ˈmenˌsēz/Definition of menses noun blood and other matter discharged from the uterus at menstruation. [treated as singular] the time of menstruation:a late mensesOrigin: late 16th century: from Latin, plural of mensis 'month'menses in other Oxford dictionaries Definition of menses in the British & World English dictionary