poker face noun
plural ∼ faces [count] : an expression on your face that does not show your thoughts or feelings — usually singular ▪ She maintained her poker face even after she heard the bad news.
— po·ker–faced 
/ˈpoʊkɚˌfeɪst/ adjective
▪ Her usually poker-faced boss gave her a big smile when he told her she was being promoted.
/ˈpoʊkɚˌfeɪst/ adjective ▪ Her usually poker-faced boss gave her a big smile when he told her she was being promoted.
