It means dead, only better.
It was made up by a genius, and is usually used in a situation where the speaker is not actually ded, but feels like they are, should be, or want to be ded.
Synonyms for ded
On this page, you will find 30 slang terms related to ded. Some of the top words include: joo ded foo, fo' sheezy, hello im dead, milkbox, Chode, and 25 more.