Green’s Dictionary of Slang

boneheaded adj.

also bonehead
[bonehead n.1 (1)]

stupid; thus boneheadedness, stupidity.

A.J. Dickson Across Plains (1929) 143: If some boneheaded mule displayed characteristic traits, the muleskinner was very expert with his long lash [DAE].
Smart Set IX. 96: You talk like a bone-headed fool! [DAE].
[UK]Wodehouse Gentleman of Leisure Ch. xxi: You bone-headed bachelors make me sick.
[US]R. Lardner You Know Me Al (1984) 169: It is a cinch that none of them bonehead nurses would have knew what to do.
[US]Wash. Herald (DC) 19 Oct. 1/7: The English-Americans are narrow, pig-headed, bone-headed and mushheaded [...] Virginia was the home of fanataicism and others the homes of bone-headedness.
[UK]Eve. Dispatch 28 June 1/5: Well, of all the bone-headed mugwumps, you take the petzel [sic].
[US]N. Putnam West Broadway 215: They are absolutely friendly except when the boneheaded Government sends soldiers in to take their children away to school by force.
[US]Times (Shreveport, LA) 29 Oct. 39/1: It wasn’t blind love — it was just bonehead infatuation.
[US]H.C. Witwer Fighting Blood 305: The Rags pulls the boss boner of a lifetime devoted to making boneheaded plays.
[US]E. Pound letter 24 Sept. in Paige (1971) 212: He will endow any number of ‘institutions’ employing any number of boneheaded dullards with ‘degrees,’ in order that they may still further befuddle the young.
[UK]D.L. Sayers Have His Carcase 242: Take off that vulgar and idiotic hat and tell me who this low-down, bone-headed, bird-witted, dissipated murderer is.
[Aus]X. Herbert Capricornia (1939) 391: You’re the sorter bonehead barsted that looks on fellers like us what have a different kinder philosophy to you as blunny criminals.
[US](con. 1918) S.J. Simonsen Soldier Bill 93: The bone-headed stunts pulled by some of the officers in charge.
[US]Lait & Mortimer USA Confidential 88: She was making one of her typical boneheaded speeches.
[US]Brides in Love I:25 July 23: My boneheaded husband thinks she means that phoney smile!
[WI]L. Barrett Rastafarians (1977) 236: Dem call dem paper tigers / Dem call dem bonehead dunces in the Queens court.
[UK]G.F. Newman You Flash Bastard 245: Your new chief, Terry, is obstinate, boneheaded, wilfully obstructive.
[US](con. c.1970) G. Hasford Short Timers (1985) 162: When I’m a civilian first class and you’re a bonehead funny gunny I’ll buy you a beer.
[SA]P. Slabolepszy ‘Return of Elvis’ Mooi Street (1994) 314: He never had to try to convince a bone-headed boss.
[UK]Observer Rev. 21 Nov. 3: I thought it was a real bonehead move on her part.
[UK]Indep. on Sun. Rev. 27 Feb. 55: From boneheaded bouncers to slick and shady rude boys.
[US]C. Hiaasen Nature Girl 123: Meanwhile your bonehead husband and his fake-Fonda lady friend just carried their bags into a mobile home.
[US]E. Drew in N.Y. Rev. of Books 17 Apr. 14/4: An action that Obama has numerous times described as ‘a mistake,’ and ‘boneheaded’.
[US]S. King Finders Keepers (2016) 185: The bonehead move was not quitting while I was ahead.
[UK]Guardian 2 May 23/3: Those responsible for bone-headed eurozone policies carry on regardless.