sliding keel vs fin keel

sliding keel and fin keel both are nouns.

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

As nouns, fin keel is a hypernym of sliding keel; that is, fin keel is a word with a broader meaning than sliding keel:

sliding keel: a retractable fin keel used on sailboats to prevent drifting to leeward
fin keel: a metal plate projecting from the keel of a shallow vessel to give it greater lateral stability

sliding keel (noun)	fin keel (noun)
a retractable fin keel used on sailboats to prevent drifting to leeward	a metal plate projecting from the keel of a shallow vessel to give it greater lateral stability