hollow vs fistulous

hollow is a noun but fistulous is not a noun.

Word	Noun	Adjective	Verb	Adverb
hollow	Yes	Yes	Yes	No
fistulous	No	Yes	No	No

hollow (noun)	fistulous (noun)
a depression hollowed out of solid matter
a small valley between mountains
a cavity or space in something

hollow (adjective)	fistulous (adjective)
not solid; having a space or gap or cavity	of or pertaining to or resembling a fistula
lacking in substance or character	hollow and tube-shaped like a reed
devoid of significance or force
as if echoing in a hollow space

hollow (verb)	fistulous (verb)
remove the interior of
remove the inner part or the core of