mum1
¦ noun Brit. informal one's mother.
--------
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.
--------
mum3
¦ verb (mums, mumming, mummed) act in a mummers' play.
Origin
ME: cf.
mum2 and Mid. Low Ger.
mummen.