1. A cephalopod mollusk of the genus nautilus, especially N. pompilius, found in the indian and pacific oceans and having a spiral, pearly-lined shell with a series of air-filled chambers. also called chambered nautilus, pearly nautilus.
2. the paper nautilus.

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.

1. the only existing genus of tetrabranchiate cephalopods. about four species are found living in the tropical pacific, but many other species are found fossil. the shell is spiral, symmetrical, and chambered, or divided into several cavities by simple curved partitions, which are traversed and connected together by a continuous and nearly central tube or siphuncle. see tetrabranchiata.
2. the argonaut; -- also called paper nautilus. see Argonauta, and paper nautilus, under paper.
3. A variety of diving bell, the lateral as well as vertical motions of which are controlled, by the occupants.

1. the Argonauta argo, or any other cephalopod believed to sail by means of the expanded tentacular arms.
2. A genus of tetrabranchiate cephalopoda, type of the Nautilacea or Nautilidæ, to which very different limits have been assigned.
3. A portuguese man-of-war. see Physalia.
4. A form of diving-bell which requires no suspension, sinking and rising by the agency of condensed air.

1. cephalopod of the indian and pacific oceans having a spiral shell with pale pearly partitions
2. a submarine that is propelled by nuclear power
3. cephalopod mollusk of warm seas whose females have delicate papery spiral shells