nautilus vs octopod

nautilus and octopod both are nouns.

Word	Noun	Adjective	Verb	Adverb
nautilus	Yes	No	No	No
octopod	Yes	No	No	No

As nouns, octopod is a hypernym of nautilus; that is, octopod is a word with a broader meaning than nautilus:

nautilus: cephalopod mollusk of warm seas whose females have delicate papery spiral shells
octopod: a cephalopod with eight arms but lacking an internal shell

nautilus (noun)	octopod (noun)
cephalopod of the Indian and Pacific oceans having a spiral shell with pale pearly partitions	a cephalopod with eight arms but lacking an internal shell
cephalopod mollusk of warm seas whose females have delicate papery spiral shells
a submarine that is propelled by nuclear power