voiding vs expelling

voiding and expelling both are nouns.

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

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

voiding: the bodily process of discharging waste matter
expelling: any of several bodily processes by which substances go out of the body

Other hypernyms of voiding include discharge, emission.

voiding (noun)	expelling (noun)
the bodily process of discharging waste matter	any of several bodily processes by which substances go out of the body