The first word returned by
"aah", even though I think it actually an interjection, I still wonder whether there lies any rationale in it; or is it just a bug?
Jokes aside, it indeed seems to be a verb in the English language. Look at this wiki entry:
Verb: aah (third-person singular simple present aahs, present participle aahing, simple past and past participle aahed)
An example would be
Everyone who came by oohed and aahed over her new appearance.