1. n : 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 [syn: menstruation, menstruum, catamenia, period, flow]

2. The catamenial or menstrual discharge, a periodic flow of blood or bloody fluid from the uterus or female generative organs.