centreboard vs sliding keel

centreboard and sliding keel both are nouns.

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

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

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

Other synonyms of centreboard include centerboard, drop keel.

centreboard (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