an expressionless face: He can tell a funny story with a poker face.
a person who has or deliberately assumes a poker face: It is impossible to tell what that poker face is really thinking.
Origin of poker face
An Americanism dating back to 1880–85Related formspok·er-faced, adjective
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for poker face
informal a face without expression, as that of a poker player attempting to conceal the value of his cards
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Idioms and Phrases with poker face
A visage lacking any expression that can be interpreted, as in Whenever Betty attended one of her children's performances, she managed to keep a poker face. This term alludes to the facial expression of a poker player who is expert at concealing his feelings about his hand. [c. 1880]
The American Heritage® Idioms Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.