1. Two groups of Cephalopods exist today: The Nautiloidea with a few species of the pearly nautilus, and the Coleoidea, containing the squids, cuttlefishes, octopods and vampire squids, which is

2. Cuttlebone definition, the calcareous internal shell of cuttlefishes, used to make powder for polishing and fed to canaries and other pet birds to supply their diet with lime

3. Any of various carnivorous marine mollusks of the class Cephalopoda, having a large head, a mouth with a chitinous beak surrounded by arms or tentacles, and in most species, an ink sac containing a dark fluid used for defense, and including the octopuses, squids, cuttlefishes, and nautiluses

4. Medical Definition of Cephalopoda : a class of mollusks including the squids, cuttlefishes, and octopuses that have a tubular siphon under the head, a group of muscular arms around the front of the head which are usually furnished with suckers, highly developed eyes, and usually a bag of inky fluid which can be ejected for defense or concealment

5. : any of a class (Cephalopoda) of marine mollusks including the squids, cuttlefishes, and octopuses that move by expelling water from a tubular siphon under the head and that have a group of muscular usually sucker-bearing arms around the front of the head, highly developed eyes, and usually a sac containing ink which is ejected for defense or concealment

6. Cephalopod definition is - any of a class (Cephalopoda) of marine mollusks including the squids, cuttlefishes, and octopuses that move by expelling water from a tubular siphon under the head and that have a group of muscular usually sucker-bearing arms around the front of the head, highly developed eyes, and usually a sac containing ink which is ejected for defense or concealment.