menstruation

The periodic discharging of the menses, the flow of blood and cells from the lining of the uterus in unfertilized females of humans and other primates.

It would seem that in Avebury, Stonehenge, and Malta the mystery cult of menstruation/mensuration reached its most consummate development.

[T]he release of semen from the penis predominantly symbolizes a forceful masculine operation, an orgasmic ‘rush’ – ejaculate refers to a sudden happening, an ejection – while the ‘loss’ of blood during menstruation is viewed as a more or less passive occurrence. Even the metaphors employed to depict these two aspects of corporeality serve to situate them on differently gendered poles. Man ‘spoofs off’ or ‘shoots his load’, while woman ‘gets her visitor’, ‘has got her monthly’.

An instance of menstruation, the part of each month during which a fertile woman menstruates.