mum Definition

ma'am
marm
mum (colloq)
contraction

1. Used as a polite or respectful form of address to a lady: madam.

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mum¹
noun

1. colloq
A mother.
2. A term used to address or refer to one's own mother. See also ma, mother, mummy. N Amer equivalent mom.

Etymology: 19c: shortened from mummy¹.

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mum²
adj

1. colloq
Silent; not speaking.
Example: keep mum about it
Thesaurus: reticent, close-lipped, close-mouthed, quiet, hushed, uncommunicative, silent; confidential, secretive, hush-hush.

Idiom: mum's the word!

colloq
An entreaty, warning or reminder to someone to keep quiet about something.

Etymology: 14c: imitating a sound produced with closed lips.

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mum³ ma'am