Is “Cumulonimbi” a Scrabble word?
Yes
CUMULONIMBI
Valid in at least one Scrabble dictionary
Valid in these dictionaries
SOWPODS / CSW
Scrabble UK & International
TWL / NWL
Scrabble North America
Large English Dictionary
General English word list
Meaning of Cumulonimbi
noun
1.A cloud, with a tall structure and a flat base, that is often associated with thunderstorms.