mouthbreather(иногда раздельно: mouth breather; иногда через дефис: mouth-breather: every single word that mouthbreather is allowed to publish is completely destroying the image of the newslettervogeler)
fuckwit("A person who is not only lacking in clue but is apparently unable or unwilling to acquire clue even when handed it on a plate in generous portions." – urbandictionary.com Vadim Rouminsky)