The Collaborative International Dictionary of English v.0.48:

Herring \Her"ring\ (h[e^]r"r[i^]ng), n. [OE. hering, AS.
   h[ae]ring; akin to D. haring, G. h[aum]ring, hering, OHG.
   haring, hering, and prob. to AS. here army, and so called
   because they commonly move in large numbers. Cf. Harry.]
   (Zool.)
   One of various species of fishes of the genus Clupea, and
   allied genera, esp. the common round or English herring
   (Clupea harengus) of the North Atlantic. Herrings move in
   vast schools, coming in spring to the shores of Europe and
   America, where they are salted and smoked in great
   quantities.
   [1913 Webster]

   Herring gull (Zool.), a large gull which feeds in part upon
      herrings; esp., Larus argentatus in America, and Larus
      cachinnans in England. See Gull.

   Herring hog (Zool.), the common porpoise.

   King of the herrings. (Zool.)
   (a) The chim[ae]ra (Chimaera monstrosa) which follows the
       schools of herring. Called also rabbit fish in the U.
       K. See Chim[ae]ra.
   (b) The opah.
       [1913 Webster]

WordNet (r) 3.0 (2006):

herring
    n 1: valuable flesh of fatty fish from shallow waters of
         northern Atlantic or Pacific; usually salted or pickled
    2: commercially important food fish of northern waters of both
       Atlantic and Pacific [syn: herring, Clupea harangus]