1.) A person that is commonly thought of as tardy, special, or slow in the head. Basically, an overall dweeb. It's a term popularly used to dis on someone to their
face without them knowing the meaning. It is also commonly shouted at someone that's saying or doing something
derp-ish, wrong, or different.
2.)
May also refer to a place or an object that is boring or highly uninteresting.
"Did you hear that Cleatus pissed on an electric fence?"
"
Yeah, he's a serious dungo!"
Or
You drive by a fat kid walking a
bike instead of riding it, so you roll down the
window and yell "dungo!!!"