bathyal district vs ocean floor

bathyal district and ocean floor both are nouns.

Word	Noun	Adjective	Verb	Adverb
bathyal district	Yes	No	No	No
ocean floor	Yes	No	No	No

As nouns, ocean floor is a hypernym of bathyal district; that is, ocean floor is a word with a broader meaning than bathyal district:

bathyal district: the steep descent of the seabed from the continental shelf to the abyssal zone
ocean floor: the bottom of a sea or ocean

Other hypernyms of bathyal district include Davy Jones's locker, Davy Jones, ocean bottom, sea bottom, sea floor, seabed.

bathyal district (noun)	ocean floor (noun)
the steep descent of the seabed from the continental shelf to the abyssal zone	the bottom of a sea or ocean