[nau.ti.lus] n, pl -lus.es or -li [NL, fr. L, paper nautilus, fr. Gk nautilos, lit., sailor, fr. naus ship] (1601) 1: any of a genus (Nautilus) of cephalopod mollusks of the So. Pacific and Indian Oceans with a spiral chambered shell that is pearly on the inside--called also chambered nautilus
2: paper nautilus