menstruation vs expelling

menstruation and expelling both are nouns.

Word	Noun	Adjective	Verb	Adverb
menstruation	Yes	No	No	No
expelling	Yes	No	No	No

As nouns, expelling is a hypernym of menstruation; that is, expelling is a word with a broader meaning than menstruation:

menstruation: the monthly discharge of blood from the uterus of nonpregnant women from puberty to menopause
expelling: any of several bodily processes by which substances go out of the body

Other hypernyms of menstruation include discharge, emission.

menstruation (noun)	expelling (noun)
the monthly discharge of blood from the uterus of nonpregnant women from puberty to menopause	any of several bodily processes by which substances go out of the body