noun. Contrary to popular anatomical notions, some skulls don't house brains--dig as deep as you like, with your trustiest bone saw, and you'll just find more bone, bone, bone. Naturally, all that bone takes a few points off the IQ, resulting in boneheadery and related conditions such as buttmunchitude.
Real citation: "Any ideas on how to correct my boneheaded mistake? And, no, the disk was not backed up - another piece of boneheadery."
(Dale M. Greer, Jan. 20, 1995, http://groups-beta.google.com/group/comp.sys.mac.system/msg/74fb7c32978144d4)
Made-up citation: "The ball-lessness and boneheadery of the Democratic party have been royally pissing me off--maybe a stiff drink and Matt Taibbi's new book Spanking the Donkey: On the Campaign Train With the Democrats will make me feel better."