centerboard vs drop keel

centerboard and drop keel both are nouns.

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

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

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

Other synonyms of centerboard include centreboard, sliding keel.

centerboard (noun)	drop 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