The Collaborative International Dictionary of English v.0.48:

Sheatfish \Sheat"fish`\, n. [Cf. dial. G. scheid, schaid,
   schaiden.] (Zool.)
   A European siluroid fish (Silurus glanis) allied to the
   cat-fishes. It is the largest fresh-water fish of Europe,
   sometimes becoming six feet or more in length. See
   Siluroid.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sheatfish
    n 1: large elongated catfish of central and eastern Europe [syn:
         European catfish, sheatfish, Silurus glanis]