- an extensive group of cirrocumulus or altocumulus clouds, especially when well-marked in their arrangement: so called because of a resemblance to the scales on a mackerel.
Origin of mackerel sky
First recorded in 1660–70
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
- a sky patterned with cirrocumulus or small altocumulus clouds
from the similarity to the pattern on a mackerel's back