Keep one's lips sealed

From Fresh Dictionary

English

Verb

keep one's lips sealed

1. ((idiomatic{{#if:|, {{{2}}}{{#if:|, {{{3}}}{{#if:|, {{{4}}}{{#if:|, {{{5}}}{{#if:|, {{{6}}}{{#if:|, {{{7}}}{{#if:|, {{{8}}}{{#if:|, {{{9}}}}}}}}}}}}}}}}}}})) To keep quiet; to keep a secret; to not tell.

   You can certainly trust me to keep my lips sealed about the matter.