shitting vs excretion

shitting and excretion both are nouns.

Word	Noun	Adjective	Verb	Adverb
shitting	Yes	No	No	No
excretion	Yes	No	No	No

As nouns, excretion is a hypernym of shitting; that is, excretion is a word with a broader meaning than shitting:

Other hypernyms of shitting include elimination, evacuation, excreting, voiding.

shitting (noun)	excretion (noun)
the elimination of fecal waste through the anus	the bodily process of discharging waste matter
	waste matter (as urine or sweat but especially feces) discharged from the body