The Collaborative International Dictionary of English v.0.48:

Echidna \E*chid"na\ ([-e]*k[i^]d"n[.a]), n. [L., a viper, adder,
   Gr. 'e`chidna.]
   1. (Gr. Myth.) A monster, half maid and half serpent.
      [1913 Webster]

   2. (Zo["o]l.) A genus of Monotremata found in Australia,
      Tasmania, and New Guinea. They are toothless and covered
      with spines; -- called also porcupine ant-eater, and
      Australian ant-eater.
      [1913 Webster]