flying boat vs seaplane

flying boat and seaplane both are nouns.

Word	Noun	Adjective	Verb	Adverb
flying boat	Yes	No	No	No
seaplane	Yes	No	Yes	No

As nouns, seaplane is a hypernym of flying boat; that is, seaplane is a word with a broader meaning than flying boat:

flying boat: a large seaplane that floats with its fuselage in the water rather than on pontoons
seaplane: an airplane that can land on or take off from water

Other hypernyms of flying boat include hydroplane.

flying boat (noun)	seaplane (noun)
a large seaplane that floats with its fuselage in the water rather than on pontoons	an airplane that can land on or take off from water

flying boat (verb)	seaplane (verb)
	glide on the water in a hydroplane