"Excuse me, I am a man."
Translation:Pardonon, mi estas viro.
You can use a noun as a verb. Or, more accurately, you can derive a verb based on a root that's a noun (or nominal root for the English majors).
For example, (from the dictionary at http://en.lernu.net/index.php):
broso (bros·o) brush
brosi (bros·i ← bros·o) (tr) to brush