(one's) lips are sealed

One will not tell anyone; one will keep this a secret. Most often used in the expression "my lips are sealed." A: "Please don't tell anyone about this, I'm so embarrassed." B: "My lips are sealed." I told him not to say anything, and he said his lips are sealed, so hopefully he'll be able to keep a secret this time. Don't worry, I won't tell anyone you're planning to resign. My lips are sealed.

See also: lip, seal

lips are sealed, one's

One will reveal nothing, especially about a secret. For example, You can trust me with the details of the lawsuit-my lips are sealed. [Early 1900s]

your lips are sealed

If you say that your lips are sealed, you mean you will keep a secret that someone has told you. As for anything told to me in confidence, well, my lips are sealed. `The Player' is worth seeing for its deeply funny ending alone but my lips are firmly sealed on that. Note: You can also say that someone has sealed lips. Most people refused to talk to him about the murder. Everywhere he went he met sealed lips and a wall of silence.

See also: lip, seal

Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012

someone's lips are sealed

a person is obliged to keep a secret.

See also: lip, seal

Farlex Partner Idioms Dictionary © Farlex 2017

(one's) lips are sealed

Used to indicate that one will not disclose a piece of information.

See also: lip, seal

American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

lips are sealed, his/my

He/I will keep this secret. Although the idea of keeping one’s mouth tightly shut is much older and sealing up someone else’s lips dates from the late 1700s, this particular expression became current only in the early twentieth century. It was much repeated by Prime Minister Stanley Baldwin when asked about the rumored abdication of King Edward VIII, who wished to (and eventually did) marry a divorced American, Wallis Simpson. See also mum's the word.