A generic and easy-to-find-a-place-for slur relating to someone who is generally an annoying waster, of little good to anyone. Usually, but not by definition, stupid as well. Think of it as a less-heard and slightly more insulting version of nobend.
People who go around urbandictionary.com giving everything a thumbs down definitely fit this category.
"Man, I just got banned from the Big Brother forums for swearing, by some jumped up twatty little fuckend of a moderator."
The exhaustion you feel after dealing with stupid and/or rude people.
Comes from "plumb tuckered out," meaning tired as hell.
I spent 20 minutes at work today explaining to a customer that he couldn't use his gift card because there was no money left on it. He kept saying "But gift cards are LIKE money". I'm dumb fuckered out; I need a beer and a nap.