Longman Dictionary of Contemporary English
Wiktionary
a. Wearing a poker face: studiously neutral in facial expression; giving nothing away.
WordNet
adj. deliberately impassive in manner; "deadpan humor"; "his face remained expressionless as the verdict was read" [syn: deadpan, expressionless, impassive, unexpressive]
Usage examples of "poker-faced".
Her inventions were seamless, she was the best poker-faced liar in the world, so there would be a kiss goodbye for stupid Crake, a smile, a wave, a closed door, and the next minute there she would be, with Jimmy.
Lizzie laughed, and Gonzales, poker-faced, looked at her and thought, yeah, this guy's laughable all right.
But Lieutenant Flynn, who'd have been a captain in the army, turned out to be a sandy-haired and politely poker-faced cuss with eyes the same shade of gray as two oysters on the half shell going stale.
Greenjeans, a proper second banana, was poker-faced but the Captain mugged each time he passed the camera.
It turned out to have all been an unfortunate mix-up, he said, completely poker-faced, but it took some time to clear up.