tight-lipped 
adjective
With the lips firmly closed, especially as a sign of suppressed emotion or determined reticence: she stayed tight-lipped and shook her head...
- I had hoped many tight-lipped elite military officers would speak sincerely about their role in the riots.
- In consequence we are becoming a tight-lipped silent majority afraid to rise above the parapet.
- As with his magic secrets Gold remains tight-lipped about his next venture.
Synonyms
reticent, taciturn, uncommunicative, unforthcoming, unresponsive, close-mouthed, close-lipped;
silent, quiet, unspeaking;
guarded, secretive, private, withdrawn, playing one's cards close to one's chest, of few words, untalkative
informal mum
- masterate
- masterbatch
- masterbatching
- master bedroom
- master builder
- master card
- Master Charge
- Mastercharge
- master chief petty officer
- masterclass
- master copy
- master craftsman
- master craftsmanship
- masterdom
- master equation
- masterer
- master eye
- master fault
- prawn and beer night
- prawn cocktail
- prawn cracker
- prawner
- prawning
- prawn-like
- prawn night