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Use "boneheaded" in a sentence
"He admitted this was what he called a boneheaded mistake."
"Instead of writing in opposition to your nemesis, write in favor of your cause; instead of calling the boneheaded author's integrity into question, extol the virtues of those who oppose that person; instead of pointing out flaws in the author's logic, create a flawless argument of your own."
"I don't think anything he did with the man classifies as boneheaded or as palling around."