Skip to main content
mum's the word

mum's the word

5 8.2
Keep quiet about a secret
  • idiom
  • Informal
translation icon : boca cerrada
  • If someone asks about our surprise party, just remember, mum's the word.
  • Okay, mum's the word
  • Yes, mum's the word
  • Mum's the word, right

Examples

Synonyms

to keep one's mouth shut
vsmum's the word
  • Informal
116 5.6

To say nothing to avoid trouble or keep a secret

is the idiomatic way to instruct someone specifically to stay silent about a secret
to keep quiet
vsmum's the word
90 2.5

To say nothing or not tell a secret

is a concise idiom used to ask specifically that a secret be kept
to keep a secret
vsmum's the word
76 2.6

To not tell anyone private information

is the idiomatic spoken prompt used to request such secrecy in conversation
to shut one's mouth
vsmum's the word
  • Informal
4 4.4

To stop talking to keep a secret or when told to be quiet

is a familiar idiom giving the same instruction to keep information secret
to keep mum
vsmum's the word
  • Informal
3 7.5

Stay quiet about something private

is a short idiom used to tell someone to keep the matter secret
to keep one's cards close to one's chest
vsmum's the word
  • Informal
1 7.6

To not tell people your plans or feelings to get an advantage

focuses more on asking others to stay silent about a secret event or fact
don't go there
vsmum's the word
  • Informal
1 9.5

A warning not to talk about a subject because it may make people angry

is a general phrase instructing silence about a secret rather than warning about upset
to keep one's cakehole shut
vsmum's the word
  • Offensive
9.9

Not say anything or tell other people

is the more idiomatic polite instruction to keep a secret rather than a crude order
loose lips sink ships
vsmum's the word
  • Informal
7.7

A warning that careless talk can cause trouble by revealing secrets

is a simple idiom asking for secrecy without stressing potential danger from talking

Antonyms

2.3

Show something that was hidden or secret

220 3.4

To say your opinion or feelings openly even when it is difficult

Surface Forms

Morphology

mum's + the + word

The phrase literally combines 'mum' (meaning 'be silent') with 'the word', so a learner who knows 'mum' in the sense 'keep quiet' could infer the meaning 'don't tell / keep quiet'. However, that sense of 'mum' is colloquial and not universally known at B1, and the fixed idiomatic phrasing (contraction/possession) makes the expression only partly predictable from its parts.

Etymology

Mum's the word may come from the old use of mum which meant 'silent'. Picture someone holding their lips shut to hide a secret. That's why mum's the word means 'keep quiet' or 'don't tell'.