Much like the Guitarface, the Pokerface is used to hide emotion during poker or any other game involving cards.
Most people are incapable of this action as they tend to snicker or jump up and down screaming "FUCK YEA I'M SO GOING TO KICK YOUR ASS WITH THIS 'GET OUT OF JAIL FREE CARD' WHEN IT'S MY TURN AGAIN YOU FUCKING PUSSY!"
An artificially maintained expression of sincerity despite the urge to space out and smile spontaneously. Similar to a poker face, except used when high on marijuana. Required when the toker doesn't want his/her high to be noticed.