centreboard vs centerboard

centreboard and centerboard both are nouns.

Word	Noun	Adjective	Verb	Adverb
centreboard	Yes	No	No	No
centerboard	Yes	No	No	No

As nouns, centreboard and centerboard are synonyms defined as:

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

Other synonyms of centreboard include drop keel, sliding keel.

centreboard (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