the periodic flow of blood and sloughed-off tissue from the uterus, discharged through the genital tract: it normally occurs about every four weeks in a woman who is not pregnant, from menarche to menopause
See menses in American Heritage Dictionary 4
(mĕnˈsēz)
plural noun(used with a sing. or pl. verb)
The monthly flow of blood and cellular debris from the uterus that begins at puberty in women and the females of other primates. In women, menses ceases at menopause. Also called catamenia.