The Collaborative International Dictionary of English v.0.48:

Saurel \Sau"rel\, n. (Zool.)
   Any carangoid fish of the genus Trachurus, especially
   Trachurus trachurus, or Trachurus saurus, of Europe and
   America, and Trachurus picturatus of California. Called
   also skipjack, and horse mackerel.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Jurel \Ju"rel\, n. (Zool.)
   A yellow carangoid fish of the Atlantic and Gulf coasts
   (Caranx chrysos), most abundant southward, where it is
   valued as a food fish; -- called also hardtail, horse
   crevall['e], jack, buffalo jack, skipjack, yellow
   mackerel, and sometimes, improperly, horse mackerel. Other
   species of Caranx (as Caranx fallax) are also sometimes
   called jurel. Juridic

The Collaborative International Dictionary of English v.0.48:

Mackerel \Mack`er*el\, n. [OF. maquerel, F. maquereau (LL.
   macarellus), prob. for maclereau, fr. L. macula a spot, in
   allusion to the markings on the fish. See Mail armor.]
   (Zool.)
   Any species of the genus Scomber of the family
   Scombridae, and of several related genera. They are finely
   formed and very active oceanic fishes. Most of them are
   highly prized for food.
   [1913 Webster]

   Note: The common mackerel (Scomber scombrus), which
         inhabits both sides of the North Atlantic, is one of
         the most important food fishes. It is mottled with
         green and blue. The Spanish mackerel (Scomberomorus
         maculatus), of the American coast, is covered with
         bright yellow circular spots.
         [1913 Webster]

   Bull mackerel, Chub mackerel. (Zool.) See under Chub.


   Frigate mackerel. See under Frigate.

   Horse mackerel . See under Horse.

   Mackerel bird (Zool.), the wryneck; -- so called because it
      arrives in England at the time when mackerel are in
      season.

   Mackerel cock (Zool.), the Manx shearwater; -- so called
      because it precedes the appearance of the mackerel on the
      east coast of Ireland.

   Mackerel guide. (Zool.) See Garfish
   (a) .

   Mackerel gull (Zool.) any one of several species of gull
      which feed upon or follow mackerel, as the kittiwake.

   Mackerel midge (Zool.), a very small oceanic gadoid fish of
      the North Atlantic. It is about an inch and a half long
      and has four barbels on the upper jaw. It is now
      considered the young of the genus Onos, or Motella.

   Mackerel plow, an instrument for creasing the sides of lean
      mackerel to improve their appearance. --Knight.

   Mackerel shark (Zool.), the porbeagle.

   Mackerel sky, or Mackerel-back sky, a sky flecked with
      small white clouds; a cirro-cumulus. See Cloud.
      [1913 Webster]

            Mackerel sky and mare's-tails
            Make tall ships carry low sails.      --Old Rhyme.
      [1913 Webster] mackerel scad

The Collaborative International Dictionary of English v.0.48:

Tuna \Tu"na\, n. [Cf. Tunny.]
   1. (Zool.) Any one of several species of large oceanic fishes
      belonging to the mackerel family Scombridae, especially
      the bluefin tuna (Thunnus thynnus, formerly Orcynus
      thynnus or Albacora thynnus), called also the common
      tunny or great tunny, a native of the Mediterranean Sea
      and of temperate parts of the Atlantic Ocean. It sometimes
      weighs a thousand pounds or more, and is caught
      commercially in large quantity for use as food; -- also
      called, especially in Britain, tunny. It is also one of
      the favorite fishes used by the Japanese in preparing
      sushi. On the American coast, especially in New England,
      it is sometimes called the horse mackerel. Another
      well-known species is the yellowfin tuna (Thunnus
      albacares) of warm seas. the See Illust. of Horse
      mackerel, under Horse.

   Note: The little tunny (Gymnosarda alletterata) of the
         Mediterranean and North Atlantic, and the long-finned
         tunny, or albacore (Thunnus alalunga) (see
         Albacore), are related species of smaller size.
         [1913 Webster +PJC]

   2. The bonito, 2.
      [1913 Webster]

   3. the meat of the tuna, used as food; -- also called tuna
      fish.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Tunny \Tun"ny\ (t[u^]n"n[y^]), n.; pl. Tunnies. [L. thunnus,
   thynnus, Gr. qy`nnos, qy^nos: cf. It. tonno, F. & Pr. thon.]
   (Zool.)
   The chiefly British equivalent of tuna; any one of several
   species of large oceanic fishes belonging to the Mackerel
   family, especially the common or great tunny (Thunnus
   thynnus syn. Albacora thynnus, formerly Orcynus thynnus)
   native of the Mediterranean Sea and the Atlantic Ocean. It
   sometimes weighs a thousand pounds or more, and is
   extensively caught in the Mediterranean. On the American
   coast it is called horse mackerel. See Illust. of Horse
   mackerel, under Horse. [Written also thynny.]
   [1913 Webster]

   Note: The little tunny (Gymnosarda alletterata) of the
         Mediterranean and North Atlantic, and the long-finned
         tunny, or albicore (Thunnus alalunga, see
         Albacore), are related species of smaller size.
         [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Albacore \Al"ba*core\, n. (Zool.)
   A name applied to several large fishes of the Mackerel family
   (Scombridae), esp. Thunnus alalunga (formerly Orcynus
   alalonga); it is a type of tuna or tunny. The name has been
   also applied to a larger related species, Thunnus thynnus
   (formerly Orcynus thynnus), common in the Mediterranean and
   Atlantic, which is called in New England the horse
   mackerel. [formerly spelled albicore.]
   [1913 Webster +PJC]

The Collaborative International Dictionary of English v.0.48:

Bluefish \Blue"fish`\, n. (Zool.)
   1. A large voracious fish (Pomatomus saitatrix), of the
      family Carangid[ae], valued as a food fish, and widely
      distributed on the American coast. On the New Jersey and
      Rhode Island coast it is called the horse mackerel, in
      Virginia saltwater tailor, or skipjack.
      [1913 Webster]

   2. A West Indian fish (Platyglossus radiatus), of the
      family Labrid[ae].
      [1913 Webster]

   Note: The name is applied locally to other species of fishes;
         as the cunner, sea bass, squeteague, etc.
         [1913 Webster]

WordNet (r) 3.0 (2006):

horse mackerel
    n 1: largest tuna; to 1500 pounds; of mostly temperate seas:
         feed in polar regions but breed in tropics [syn: bluefin,
         bluefin tuna, horse mackerel, Thunnus thynnus]
    2: large elongated compressed food fish of the Atlantic waters
       of Europe [syn: horse mackerel, saurel, Trachurus
       trachurus]
    3: a California food fish [syn: horse mackerel, jack
       mackerel, Spanish mackerel, saurel, Trachurus
       symmetricus]