Definition of have bats in the (or one's) belfry in US English:

have bats in the (or one's) belfry

phrase

informal
  • Be eccentric or crazy.

    • ‘The rumor is that Maggie has bats in her belfry?’
    • ‘It looks like I have bats in my belfry with that Halloween decoration hanging on the guillotine.’
    • ‘The man obviously had bats in his belfry for making such a ludicrous statement.’
    • ‘Not sure if he had bats in his belfry.’
    • ‘All I know is that if I had bats in my belfry I'd buy a couple of big strings of garlic (I hate vampires) and a big fly swatter.’
    insane, mentally ill, certifiable, deranged, demented, of unsound mind, out of one's mind, not in one's right mind, sick in the head, not together, crazy, crazed, lunatic, non compos mentis, unbalanced, unhinged, unstable, disturbed, distracted, stark mad, manic, frenzied, raving, distraught, frantic, hysterical, delirious, psychotic, psychopathic, mad as a hatter, mad as a march hare, away with the fairies, foaming at the mouth
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