What's the plural form of horsebreaking? Here's the word you're looking for.
Answer
The noun horsebreaking can be countable or uncountable.
In more general, commonly used, contexts, the plural form will also be horsebreaking.
However, in more specific contexts, the plural form can also be horsebreakings e.g. in reference to various types of horsebreakings
or a collection of horsebreakings.