Answer: I'm thinkin' "word is not a noun", but maybe I'm rusty :p
Step-by-step explanation:
Wellll, a direct object from what I'm understanding is a NOUN that takes the action of a verb. It's one of those things that answers the "what" or "who" questions. Like "The students ate cake." The students ate what? cake. For this question in particular, dirty doesn't seem like a noun.