mammatus

[ muh-mah-tuhs, muh-mat-uhs, mam-uh-tuhs ]

noun

, Meteorology.

, plural mam·ma·tus.

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: mamma ²( def 2 ).

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

Word History and Origins

Origin of mammatus¹

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