mum is the word Idiom
mum is the word|mum|word
You must keep the secret; keep silent; don't tell anyone.

Often used as an interjection.
We are planning a surprise party for John and mum is the word. "Mum is the word!" the robber captain told his men.mum is the word|mum|word
You charge accumulate the secret; accumulate silent; don't acquaint anyone.

Often acclimated as an interjection.
We are planning a abruptness affair for John and mum is the word. "Mum is the word!" the bandit captain told his men. Dictionary