Is the word exhale a noun?

No, "exhale" is primarily a verb. It describes the act of breathing out.

While it's possible to use "exhale" as a noun in some very specific contexts (e.g., "The doctor listened for his patient's exhale"), it's not a common usage.

If you want to use "exhale" as a noun, you could use a phrase like "the act of exhaling" or "the process of exhaling."