Dumb
Dumb adjective - Deliberately refraining from speech.
Usage example: the mayor has chosen to remain dumb about her activities that night
Mum is a synonym for dumb in silent topic. In some cases you can use "Mum" instead an adjective "Dumb", when it comes to topics like words, unable to speak. informal substitute
Mum
Mum adjective - Deliberately refraining from speech.
Usage example: kept mum about the surprise bridal shower
Mutual synonyms
Both words in one sentence
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Subverted in a World War II "Careless Talk Costs Lives" poster, which showed a sexy blonde surrounded by off-duty forces personnel and the caption "Keep mum - she's not so dumb".
Source: Dumb Blonde -
Thank you, god, for fixing the cataracts of Sam's mum / I had no idea but it's suddenly so clear now / I feel like such a cynic how could I have been so dumb?
Source: Motor Mouth - The Danish translation of Robert Harris' WWII novel Enigma translated the text of a classic propaganda poster warning people to beware of enemy spies ("Keep mum, she's not so dumb") as "Keep Mother, she is not so stupid".
Cite this Source
Mum and Dumb. (2016). Retrieved 2026, July 21, from https://thesaurus.plus/related/dumb/mum
Dumb & Mum. N.p., 2016. Web. 21 Jul. 2026. <https://thesaurus.plus/related/dumb/mum>.
Mum or Dumb. 2016. Accessed July 21, 2026. https://thesaurus.plus/related/dumb/mum.
Google Ngram Viewer shows how "dumb" and "mum" have occurred on timeline