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