drop keel vs centreboard

drop keel and centreboard both are nouns.

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

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

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

Other synonyms of drop keel include centerboard, sliding keel.

drop keel (noun)	centreboard (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