any mollusc of the Nautiloidea, a group of cephalopods that includes the pearly nautilus and many extinct forms
adjective
2.
of, relating to, or belonging to the Nautiloidea
nautiloid in American English
(ˈnɔtəlˌɔɪd)
noun
any of a subclass (Nautiloidea) of cephalopods with chambered, coiled, or straight external shells: the nautiluses are the only remaining representatives