sinkhole vs swallow hole

sinkhole and swallow hole both are nouns.

Word	Noun	Adjective	Verb	Adverb
sinkhole	Yes	No	No	No
swallow hole	Yes	No	No	No

As nouns, sinkhole and swallow hole are synonyms defined as:

sinkhole and swallow hole: a depression in the ground communicating with a subterranean passage (especially in limestone) and formed by solution or by collapse of a cavern roof

Other synonyms of sinkhole include sink.

sinkhole (noun)	swallow hole (noun)
a depression in the ground communicating with a subterranean passage (especially in limestone) and formed by solution or by collapse of a cavern roof	a depression in the ground communicating with a subterranean passage (especially in limestone) and formed by solution or by collapse of a cavern roof