flushless toilet vs crapper

flushless toilet and crapper both are nouns.

Word	Noun	Adjective	Verb	Adverb
flushless toilet	Yes	No	No	No
crapper	Yes	No	No	No

As nouns, crapper is a hypernym of flushless toilet; that is, crapper is a word with a broader meaning than flushless toilet:

flushless toilet: a toilet that relies on bacteria to break down waste matter (instead of using water)
crapper: a plumbing fixture for defecation and urination

Other hypernyms of flushless toilet include can, commode, pot, potty, stool, throne, toilet.

flushless toilet (noun)	crapper (noun)
a toilet that relies on bacteria to break down waste matter (instead of using water)	a plumbing fixture for defecation and urination