What is the shape of a culumbus cloud?

They are puffy, like cotton balls. Not in any any particular shape, just round(ish).
Gigantic white towers of cloud with dark grey bases, sometimes with flattened tops appearing like a pancake or an anvil
A cumulonimbus formation is tall and billowing, with an anvil-shaped top.
Cumulonimbus clouds have flat tops and bottoms, giving them an anvil-like appearance.
stormy weather, most likely low pressures system, and gusty... and occurs during a cold front. :D