col vs water gap

col and water gap both are nouns.

Word	Noun	Adjective	Verb	Adverb
col	Yes	No	No	No
water gap	Yes	No	No	No

As nouns, water gap is a hyponym of col; that is, water gap is a word with a more specific, narrower meaning than col:

col: a pass between mountain peaks; geomorphological term for the lowest point on a mountain ridge between two peaks
water gap: a pass in a mountain ridge through which a stream flows

Other hyponyms of col include wind gap.

col (noun)	water gap (noun)
a pass between mountain peaks; geomorphological term for the lowest point on a mountain ridge between two peaks	a pass in a mountain ridge through which a stream flows