" closemouthed "

1: given to keeping one's activities hidden from public observation or knowledge;

  * e.g., " ... he remained closemouthed about their activities "

•  Synonyms : 

•  close,

•  dark,

•  reticent,

•  secretive,

•  tight-mouthed,

•  uncommunicative

•  Antonyms : 

•  communicative,

•  open

2: tending not to speak frequently (as by habit or inclination);

  * e.g., " ... encourage the closemouthed children to speak up and not be shy "

•  Synonyms : 

•  dumb,

•  laconic,

•  reserved,

•  reticent,

•  silent,

•  taciturn,

•  tight-lipped,

•  uncommunicative

•  Antonyms : 

•  blabby,

•  chatty,

•  communicative,

•  conversational,

•  gabby,

•  garrulous,

•  loquacious,

•  motormouthed,

•  mouthy,

•  talkative,

•  talky,

•  unreserved