[TButtrick]

Well you could write "dumbass" or "dumb-ass" hyphenated. The benefit of using "dumb-ass" hyphenated is that you can interject additional adjectives in between to further describe the noun. Here's an example:

You dumb, mother f***ing ass, you have no idea what the f**k you're talking about you dumb c**k sucking a**hole. Very effective.