A retard. Someone mentally challenged.
Look at that dernt! He can barely grunt what with all that drooling he's doing!
A sound effect used to describe a unpleasant occurance or appearance etc. Much like the sound of a foghorn.
Someone extremely hungover walks into the room and the only way to describe them is simply "dernt".
Fat or Large. Comes from the drum sound effect often associated with a large zepplin or airship coming into a scene in older movies. Same sound can also be heard in Super Mario Brothers 3, on any airship level.
Damn that football player is dernt.