The Collaborative International Dictionary of English v.0.48:

Gymnotus \Gym*no"tus\ (j[i^]m*n[=o]"t[u^]s), n. [NL., fr. Gr.
   gymno`s naked + nw^tos the back: cf. F. gymnote.] (Zool.)
   A genus of South American fresh-water fishes, including the
   Gymnotus electricus, or electric eel. It has a greenish,
   eel-like body, and is possessed of electric power.
   [1913 Webster]

         One fearful shock, fearful but momentary, like that
         from the electric blow of the gymnotus.  --De Quincey.
   [1913 Webster]