- belonging or pertaining to the Nautiloidea (Tetrabranchiata), a subclass or order of cephalopods with four gills, including the pearly nautilus and numerous fossil forms.
- of, relating to, or belonging to the Tetrabranchiata, a former order of cephalopod molluscs having four gills and including the pearly nautilus
- any mollusc belonging to the Tetrabranchiata
