The name given to the facial area of a person who has an abnormally large and round face. As implied in the name, the circular face will resemble a pie, or a perfect circle drawn carefully with a compass in maths. A person with a pie face is likely to be mocked incessantly by 'friends', and subsequently may find it hard to talk to people without them thinking they are talking to a floating pastry.
'Good heavens, have you seen how round Emma's face is?!'
'Yeah, massive pie face.'