A cephalopod, belonging to the genus Loligo and related genera. There are many species. They have a sack of inklike fluid which they discharge from the siphon tube, when pursued or alarmed, in order to confuse their enemies. Their shell is a thin horny plate, within the flesh of the back, shaped very much like a quill pen. In America they are called squids. See Squid.  [1913 Webster]