It's actually disastrously bad for the wack

from Eminem – Rap God Lyrics on Rap Genius

Meaning

Dizaster-ously bad. Canibus, who Eminem has had beef with in the past, agreed to battle a battle rapper named Dizaster, but showed up with a messed up shoulder. He got destroyed and with all the pain couldn’t really lyrically retaliate. He forgot his lines and ultimately pulled out his notebook to finish the battle. (It was painful to watch.)

http://youtu.be/VZVMvxYQgdc?t=1m47s

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