Source : Webster's Revised Unabridged Dictionary (1913)

Octopus \Oc"to*pus\, n. [NL. See {Octopod}.] (Zo["o]l.)
   A genus of eight-armed cephalopods, including numerous
   species, some of them of large size. See {Devilfish},

Source : WordNet®

octopus
     n 1: tentacles of octopus prepared as food
     2: bottom-living cephalopod having a soft oval body with eight
        long tentacles [syn: {devilfish}]
     [also: {octopi} (pl)]