drop keel vs sliding keel

drop keel and sliding keel both are nouns.

Word	Noun	Adjective	Verb	Adverb
drop keel	Yes	No	No	No
sliding keel	Yes	No	No	No

As nouns, drop keel and sliding keel are synonyms defined as:

drop keel and sliding keel: a retractable fin keel used on sailboats to prevent drifting to leeward

Other synonyms of drop keel include centerboard, centreboard.

drop keel (noun)	sliding keel (noun)
a retractable fin keel used on sailboats to prevent drifting to leeward	a retractable fin keel used on sailboats to prevent drifting to leeward