What does zipper your mouth mean?

"Zipper your mouth" is a slang expression meaning to shut up or stop talking. It's often used in a playful or teasing way, but it can also be used more aggressively to tell someone to be quiet.

It's similar to other expressions like:

* Zip it!

* Shut your face!

* Pipe down!

* Hold your tongue!

The expression gets its name from the act of zipping a zipper closed, which effectively silences any sound coming from inside.