Definition of mackerels:
(n) :
Certain smaller edible fish, principally true mackerel and Spanish mackerel in family Scombridae, often speckled,
(n) :
A true mackerel, any fish of tribe Scombrini (Scomber spp., Rastrelliger spp.)
(n) :
typically Scomber scombrus in the British isles.
(n) :
Certain other similar small fish in families Carangidae, Gempylidae, and Hexagrammidae.
(n) :
(chiefly attributive, of clouds, the sky, etc) A regular pattern, similar to fish scales, of undulating small clouds with sky visible between them.
(n) :
(obsolete) A pimp; also, a bawd.