Synonyms for Keep mum:

• n.

  •belt up (noun)
  • belt up.
  •be quiet (noun)
  • be quiet.
  •button up (noun)
  • button up.
  •clam up (noun)
  • clam up.
  •close up (noun)
  • close up.
  •dummy up (noun)
  • dummy up.

• Other synonyms:

  •
  • hold out on.
  •
  • classify.
  •
  • conceal.
  •
  • keep back,
  • suppress.
  •
  • hide.
  •
  • guard.

Antonyms for Keep mum:

• v.

  • Other antonyms:
    open up.