If something unlucky, ridiculous, incredible, etc were to happen, you yell this. The number of times you say "dirtay" determines how bad the event was (ex: 10 dirtays is very bad)
(Z.D. shoots a basketball, it hits the rim, but rolls in and out)
Z.D.: (Screaming) DIRTAY DIRTAY DIRTAY DIRTAY!
Mullet: (rofling) Dirtay Dirtay!