The infinitive form of the verb is: nagegon
v. V-fin. to sweat
From Dothraki Wiki
Edit: I am still trying to understand how this vocabulary page works, and I can see there is a link for this verb that indicates the "High Valyrian Verb Tables", putting it between the vowel-final verbs, and exactly in the E-stems verbs. So, there are different verb stems and not only vowel-final verbs, also there are consonant-final verbs and irregular verbs.