[mack.er.el] n, pl mackerel or mackerels [ME makerel, fr. MF] (14c) 1: a scombroid bony fish (Scomber scombrus) of the No. Atlantic that is green above with dark blue bars and silvery below and is one of the most important food fishes
2: any of a family (Scombridae) of fishes including the common mackerel; esp: a comparatively small member of this group as distinguished from a bonito or tuna