dime-dropper

dime-dropper

One who snitches or informs on someone to a person of higher authority. Originally street slang for someone who informs to the police, it refers to the old price of using a public payphone (10 cents). Primarily heard in US, South Africa. I bet Timmy's the dime-dropper—he's such a teacher's pet, always ready to tattle on any of the other students he thinks are misbehaving. He knew he was facing 10 years in prison, so he agreed to be a dime-dropper for the police in exchange for a lighter sentence.
Farlex Dictionary of Idioms.

dime-dropper

n. an informer. (see also drop a dime.) I think that Taylor is the dime-dropper who caused the roust.
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
See also:
  • dropper
  • snitch
  • accompany (one) on a/(one's) journey
  • accompany on a journey
  • a stranger to (someone or something)
  • be out of (one's) league
  • be out of somebody's league
  • be in bad with (someone)
  • bell, book, and candle
  • bell, book, and candle things that are miraculous or that signal that
References in periodicals archive
I told them that we thrive on tips from dime-droppers, but how we must be conscious of the motives of those who drop those dimes.
Debating how and why journalists do what they do