Definition of drop a (or the) dime on someone in US English:

drop a (or the) dime on someone

phrase

informal
  • Inform on someone.

    • ‘I believe that he is one of the senior administration officials who dropped the dime on her.’
    • ‘What will ultimately happen to the teenage high school student is still up in the air, but the fact of the matter is that he confessed to the crime after being turned in, and those who dropped dime on him did so for the reward money.’
    • ‘We also wish to thank the kindred spirit who dropped the dime on him.’
    • ‘He would eventually hit the 619 out of no where, then dropped the dime on him for the pinfall victory.’
    • ‘Even if they didn't reveal your identities up front, once the substance of the complaint becomes clear, he is bound to know who dropped the dime on him.’
    inform, inform on someone, tell tales, tell tales on someone
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