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Dedy is a word meaning someone or something is cool. It came from Thetford in the late 90's and since then has been widely used through out England in the youth cultures.
It can be used in a sarcastic way to someone ugily, or silly looking, as if to say they are so uncool.

It is prounounced det - de.
It is commonly misspelled dede
"You are dedy"
"Look at your dedy head"
"Why are you so dedy"
by James Moore November 07, 2006