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]

The Collaborative International Dictionary of English v.0.48:

Siluroid \Si*lu"roid\, n. [Silurus + -oid.] (Zool.)
   Belonging to the Siluroidei, or Nematognathi, an order of
   fishes including numerous species, among which are the
   American catfishes and numerous allied fresh-water species of
   the Old World, as the sheatfish (Silurus glanis) of Europe.
   -- n. A siluroid fish.
   [1913 Webster]

WordNet (r) 3.0 (2006):

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