Definition of holy mackerel
- Holy mackerel! You got your hair cut!
: exalted or worthy of complete devotion as one perfect in goodness and righteousness
: devoted entirely to the deity or the work of the deity
: a scombroid fish (Scomber scombrus of the family Scombridae) of the North Atlantic that is green above with dark blue bars and silvery below and is a commercially important food fish
: any of various fishes (such as the wahoo and king mackerel) in the same family as the mackerel especially when distinguished from the related bonito or tuna by a comparatively smaller size
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