An obsolete term for cumulonimbus mammatus, it is a portion of a cumulonimbus cloud that appears as a pouch or udder on the under surface of the cloud. Although they do not cause severe weather, they often accompany storms.
MAMMATOCUMULUS
Meaning of MAMMATOCUMULUS in English
Weather and meteorology English vocabulary. Английский словарь погоды и метеорологии . 2012