nautilus

noun

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.

   “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.”

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