The Collaborative International Dictionary of English v.0.48:

Diodon \Di"o*don\, n. [Gr. di- = di`s- twice + 'odoy`s,
   'odo`ntos, a tooth: cf. F. diodon.]
   1. (Zool.) A genus of spinose, plectognath fishes, having the
      teeth of each jaw united into a single beaklike plate.
      They are able to inflate the body by taking in air or
      water, and, hence, are called globefishes,
      swellfishes, etc. Called also porcupine fishes, and
      sea hedgehogs.
      [1913 Webster]

   2. (Zool.) A genus of whales.
      [1913 Webster]