Delilah: What are you doing?
Janet: Nothing! Nothing at all!
Delilah: You know, you have a terrible poker face. Come on, spill it.

A poker face is an emotionless expression that doesn’t give anything away to other people. When playing poker, you don’t want the other players to know whether your cards are good or not, so you put on your poker face. If you don’t have a good poker face, you will have a hard time lying to or deceiving people.