sliding keel vs centerboard

sliding keel and centerboard both are nouns.

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

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

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

Other synonyms of sliding keel include centreboard, drop keel.

sliding keel (noun)	centerboard (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