Obstinate idiot, that goes on doing something despite obvious failure. Serves as a common insult for someone who is exceptionally stupid, dense, or slow on the uptake, metaphorically drawing a parallel to a blunt object or someone whose brain has been hollowed out.
Муж её, долбень, в Афгане и позвонить оттуда не-воз-мож-но! А что было у тебя с этой козой, так забудь! Ты ей — не в масть. Теперь она со мной чалится. Не лезь к ней!
Her husband, the dumbass, is in Afghanistan, and calling from there is im-pos-sible! And whatever you had with that goat, forget it! You’re not her type. Now she’s chilling with me. Stay away from her!
(Олег Блоцкий, Телефонный разговор, 2004)
