A person of low intelligence, extreme annoying tendencies, and a severe lack of talent; completely oblivious to their faults.
"Phillip, you completed your exam upside down, I'm afraid I'm going to have to fail you on account of being a dunkel," said Mr. Steinberg
"Dude, when I told you to get us a pizza, I didn't mean to go out and buy a freakin' Lunchable. You're a total dunkel!"
You're such a dunkel that before you were born, you're mom asked if you were going to be a boy or a girl, and the doctor replied, "neither, you're giving birth to a healthy baby dunkel."