What is the collective noun used for cotton balls?

There isn't a specific, widely recognized collective noun for cotton balls.

You could use a general collective noun like:

* Pile of cotton balls

* Bunch of cotton balls

* Heap of cotton balls

* Clump of cotton balls

You could also be creative and use a descriptive phrase like:

* Fluff of cotton balls

* Cloud of cotton balls

Ultimately, the best choice depends on the context of your writing.