From Longman Dictionary of Contemporary Englishpoker-facedˌpoker-ˈfaced adjective EXPRESSION ON somebody'S FACEshowing no expression on your face a poker-faced officer —poker face noun [singular]
Examples from the Corpus
poker-faced• The checkers at the airport were poker-faced but affable.• He champed on his gum in time to the music, and kept a poker-faced expression.• Throughout his treatise Pope maintains the pose of the poker-faced instructor.• Not even Will Rogers could make the poker-faced President laugh. 