have a screw loose

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have a screw loose (third-person singular simple present has a screw loose, present participle having a screw loose, simple past and past participle had a screw loose)

1. (slang) To be insane, irrational, or eccentric.
   • 1871 July – 1873 February, Anthony Trollope, “The Major”, in The Eustace Diamonds. A Novel, New York, N.Y.: Harper & Brothers, […], published 1872, →OCLC, page 306, column 1:

     Richard, glorious in new livery, [...] went with his sad message, first to the church and then to the banqueting-hall in Albemarle Street. "Not any wedding?" said the head-waiter at the hotel. "I knew they was folks as would have a screw loose somewheres. [...]"

   • 1916, Eleanor H. Porter, chapter 22, in Just David:

     "You know he really has got a screw loose in his head somewheres, an' there ain't any one but what says he's the town fool, all right."

   • 2010 July 16, Alessandra Stanley, “Television: Back to Work for ‘Mad Men’”, in New York Times, retrieved 16 June 2016:

     Pete Campbell (Vincent Kartheiser) would be just another irritating office brown-noser, a prep school Sammy Glick, except that he too has a screw loose and a mystical rapport with firearms.

   • 2016 September 23, Dan Shive, El Goonish Shive (webcomic), Comic for Friday, Sep 23, 2016:

     "A successful murder has to be 'attempted' in the first place." "We both know what matters here is how you perceive the meaning." "Any immortal who considers that a loophole has a screw loose." "For all I know, your screws..." "I vow to not do anything with the intent of Elliot getting killed, okay? Leave my screws out of this."

• screw loose

• have one's head screwed on
• screwball
• screwy