mum1
¦ noun Brit. informal one's mother.
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mum2
¦ adjective (in phr. keep mum) informal remain silent so as not to reveal a secret.
Phrases
mum's the word do not reveal a secret.
Origin
ME: imitative of a sound made with closed lips.
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mum3
¦ verb (mums, mumming, mummed) act in a mummers' play.
Origin
ME: cf.
mum2 and Mid. Low Ger. <
i>mummen
i>.