Noun. An obstreperous mouth.

Hark! Shut your obstropolos.
Ulysses, James Joyce (1922) 

Leave it to the OED to give you a definition that you probably need to look up.

Obstreperous: adj. Clamorous, noisy, vociferous. Give yourself a pat on the back if you already knew obstreperous. You are a true word-nerd.

This could be a good word to use when you feel like coming off like a total snob to someone who just won’t be quiet. Just say, “Shut your obstropolos,” and you’ll no longer be plagued by their presence. Works well for co-workers, in-laws, and tele-marketers.