mum

Someone who's mum has nothing to say, especially on a particular subject. If you agree to keep someone's secret, you could tell them, "Mum's the word!"

A shy child who's new at school might stay mum all day, and even your most talkative friend might remain mum on controversial topics like religion and politics. In many parts of the world, mum is also a nickname for your mother — and it's also a nickname for the flower called a chrysanthemum. The "quiet" meaning of mum comes from Old English, inspired by the "mmm" sound you make when your lips are closed.

Primary Meanings of mum

1.
adjn
failing to speak or communicate etc when expected to
secrecy
2.
n
informal terms for a mother
3.
n
of China
Full Definitions of mum
1

adj failing to speak or communicate etc when expected to

Synonyms:
silent
incommunicative, uncommunicative
not inclined to talk or give information or express opinions

n secrecy

mum's the word”
Type of:
secrecy, secretiveness, silence
the trait of keeping things secret
2

n informal terms for a mother

Synonyms:
ma, mama, mamma, mammy, mom, momma, mommy, mummy
Type of:
female parent, mother
a woman who has given birth to a child (also used as a term of address to your mother)
3

n of China

Synonyms:
Chrysanthemum morifolium, Dendranthema grandifloruom, florist's chrysanthemum, florists' chrysanthemum
Type of:
chrysanthemum
any of numerous perennial Old World herbs having showy brightly colored flower heads of the genera Chrysanthemum, Argyranthemum, Dendranthema, Tanacetum; widely cultivated

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