n. 笨蛋

[ noun ]
a stupid person; these words are used to express a low opinion of someone's intelligence
<noun.person>

bonehead \bone"head`\ n.
a person of low intelligence; a dunce; a blockhead; -- used
deprecatingly to express a low opinion of someone's
intelligence or capabilities.

Syn: dunce, dunderhead, numskull, blockhead, lunkhead,
hammerhead, knucklehead, loggerhead, muttonhead,
shithead, fuckhead.
[WordNet 1.5]