You're a Dumb 

when the person does something so stupid that you can use the word dumb as a noun.

Jordy: "so, what your ethnicity?"

Larry: "My great Grandparents Immigrated here from Germany"

Jordy "oh, so you're from Germany? That makes you Germanese, right?"

Larry "... You're a Dumb"

You're a Dumb by Ira Sex Ira 696969 November 3, 2009

You're such a dumbledore 

Using the wizard name from harry potter to call someone dumb.

"Why would you do something like that? You're such a dumbledore I swear."

You're such a dumbledore by Elizapple August 8, 2016