let something slip
• reveal something inadvertently in the course of a conversation.
• "Alex had let slip he was married"
Similar:
reveal,
disclose,
divulge,
let out,
give away,
come out with,
blurt out,
leak,
give the game away,
let on,
blab,
let the cat out of the bag,
spill the beans,
blow the gaff,
discover,
Opposite:
keep something secret,
• release a hound from the leash so as to begin the chase.
• "let slip the dogs of war"
