have a loose tongue

have a loose tongue

To speak too frequently and/or without discretion, especially as when unintentionally revealing private or sensitive information to others. You have a very loose tongue. You'd do well to learn to keep your mouth shut! The details of this project are extremely confidential, so make sure you don't have a loose tongue about it.
See also: have, loose, tongue
Farlex Dictionary of Idioms.

have a loose ˈtongue

talk too much, especially about things that are private: Be careful what you tell Sam — she’s got a very loose tongue, you know.
See also: have, loose, tongue
Farlex Partner Idioms Dictionary
See also:
  • loose lip(s)
  • loose talk
  • foot-in-mouth disease
  • fall through the cracks
  • foot in one's mouth, put one's
  • put (one's) foot in (one's) mouth
  • put foot in mouth
  • slip between the cracks
  • slip through the cracks
  • slip through the net