let (someone) in on (something)

to tell someone a secret.

Bill, could you let me in on your techniques for getting along with girls?

The plan was so well guarded they only let three people in on it.

Related vocabulary: horn in on someone/something, in on something

• If someone thinks something, they've got another thing coming!
• If someone thinks something, they've got another think coming!
• If someone thinks, they've got another thing coming!
• If someone thinks, they've got another think coming!
• If the cap fits .
• If the cap fits wear it.
• if the going gets rough
• if the going gets tough
• if the worst comes to the worst
• If thinks something, they've got another thing coming!
• If thinks something, they've got another think coming!
• If thinks, they've got another thing coming!
• If thinks, they've got another think coming!
• if worst comes to worst
• If you believe that, you'll believe anything!
• if you can help it
• If you can't beat 'em!
• If you can't beat 'em, join 'em!
• If you can't stand the heat, get out of the kitchen.
• if you catch my drift
• if you get my drift
• If you pay peanuts, you get monkeys.
• if you play cards right
• if you play your cards right
• If you've got it, flaunt it!