What is the verb form of enthusiasm?

There isn't a direct verb form of "enthusiasm." However, you can express the action of being enthusiastic with these verbs:

* Enthusiastically (adverb): This can be used to modify another verb, showing the action is done with enthusiasm. For example: "He enthusiastically joined the project."

* Be enthusiastic about: This phrase expresses the feeling of enthusiasm towards something. For example: "She is enthusiastic about her new job."

* Show enthusiasm: This phrase describes the act of expressing enthusiasm. For example: "The students showed enthusiasm for the field trip."

You can also use verbs related to enthusiasm, such as:

* Excite: To make someone feel enthusiastic.

* Inspire: To fill someone with enthusiasm.

* Motivate: To encourage someone to be enthusiastic.

The best verb to use will depend on the specific context.