keep (something) under (your) hat

to keep something secret.

I've got some interesting news, but you must promise to keep it under your hat for the moment.

• Time flies when you're having fun.
• time hangs heavy
• time hangs heavy on hands
• time hangs heavy on someone's hands
• time is on side
• time is on your side
• time is ripe
• time is up
• time lies heavy
• time lies heavy on hands
• time lies heavy on someone's hands
• time on hands
• time on your hands
• time-out
• times have changed
• time's up
• Time will tell.
• time will tell
• tin ear
• tin god
• tinkle the ivories
• tip hand
• tip off
• tip off someone
• tip of the iceberg