ENGLISH
REFERENCE

mum

adj.
US //ˈməm// UK //mˈʌm// mum
  1. 1 silent (adj.)
    C1 Advanced Informal

    staying quiet or keeping a secret.

    remaining silent or refractive to disclosure; typically used in the fixed phrase 'mum's the word'.

    Example

    I promised to keep mum about the surprise party until Saturday.

    Example

    The witnesses decided to keep mum during the initial investigation, fearing that any statement might lead to further complications.

    Usage

    Commonly follows the verb 'keep'.
Etymology 1

Alternative form of mam, or an abbreviation of mummy. Compare mom, mama.

Etymology 2

Abbreviation of chrysanthemum.

Etymology 3

From Middle English mum or mom (“silent”), reminiscent of the sound made when gagged or with a hand over one's mouth. Perhaps related to dated German Mumme (“mask”).

Etymology 4

From German Mumme.

Etymology 5

A variant of ma'am.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

Word family

Last updated June 19, 2026