Pronunciation: (nôt'l-us, not'-),[key] —n., —pl.nau•ti•lus•es, nau•ti•liPronunciation: (nôt'l-ī", not'-)[key]for 1, 2. 1. Also called chambered nautilus, pearly nautilus. any cephalopod of the genus Nautilus, having a spiral, chambered shell with pearly septa.
2. See paper nautilus. 3. (cap.) the first nuclear-powered submarine launched by the U.S. Navy.