mammatus

American  

[muh-mah-tuhs, muh-mat-uhs, mam-uh-tuhs] / məˈmɑ təs, məˈmæt əs, ˈmæm ə təs /

noun

Meteorology.

plural

mammatus

1. a formation of pouchlike clouds created within a cumulonimbus and hanging from its underside, typically as a short-lived phenomenon associated with severe weather.

   The spectacle of mammatus is the opposite of fluffy, floating clouds—it’s like “thundercloud udders” filled with downward-pulling cold moisture.

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Etymology

Origin of mammatus

Coined in 1894 by English meteorologist William Clement Ley (1840–1896); from Latin: “breastlike, having breasts,” adjective derivative of mamma mamma ² ( def. )

Example Sentences

Some of the best examples of mammatus can be seen when the sun is low in the sky, casting light on the underside of the cloud and showing up the 'udders'.

From BBC • Feb. 26, 2025

Unusual mammatus clouds were spotted on Wednesday morning in parts of the United Kingdom.

From BBC • Feb. 26, 2025

If you see mammatus cloud like this, it is a sure sign of impending heavy rain, hail or a big thunderstorm.

From BBC • Feb. 26, 2025

The name mammatus comes from the Latin mamma which means 'udder' or 'breast'.

From BBC • Feb. 26, 2025

These mammatus clouds, underneath a cumulonimbus cloud, were spotted by Patsy Hampson in Douglas, Isle of Man.

From BBC • Jul. 30, 2011