nautilus

plural nautiluses · plural nautili

1. A marine mollusc, of the family Nautilidae native to the Pacific Ocean and Indian Ocean, which has tentacles and a spiral shell with a series of air-filled chambers, of which Nautilus is the type genus.

   Living species of the externally shelled nautiluses do not possess an ink sac.

   2017 August 9, Mark Carnall, “Why do cephalopods produce ink? And what's ink made of, anyway?”, in The Guardian, archived from the original on 15 Mar 2023

   2 more examples

   He was still prepared to go on collecting all that life could offer, like a chambered nautilus patiently adding new cells to its slowly expanding spiral.

   1956, Arthur C. Clarke, The City and the Stars, page 44

   Nautilidan cephalopods, represented today by the six living species of nautilus are thought to have diverged from other nautiloids in the Devonian period.

   2016 August 17, Mark Carnall, “I, for one, welcome our new cephalopod overlords ... but what are they?”, in The Guardian, archived from the original on 31 Mar 2019

2. A kind of diving bell that sinks or rises by means of compressed air.
3. inexactA paper nautilus (actually an octopus).