swallow hole vs sinkhole

swallow hole and sinkhole both are nouns.

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

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

swallow hole and sinkhole: 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 swallow hole include sink.

swallow hole (noun)	sinkhole (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