When a woman menstruates, a flow of blood comes from her womb. Women menstruate once a month unless they are pregnant or have reached the menopause.
例句
Lean hard-training women athletes may menstruate less frequently or not at all.身材瘦削而且训练艰苦的女运动员行经可能不那么频繁，或者根本不来月经。
英汉词典释义
n.
月经;行经;月经期间
the taboos surrounding menstruation与月经相关的禁忌
英英词典释义
Noun
1. the monthly discharge of blood from the uterus of nonpregnant women from puberty to menopause;
"the women were sickly and subject to excessive menstruation""a woman does not take the gout unless her menses be stopped"--Hippocrates"the semen begins to appear in males and to be emitted at the same time of life that the catamenia begin to flow in females"--Aristotle