I like the definition for custards and creams out of "On Food And Cooking" by Harold McGee:
'A mixture of eggs and liquid cooked that sets into a solid gel."
Technically a frozen custard and pastry cream are the same thing, and neither of them is a custard since a custard is a mixture of eggs and liquid cooked without stirring and results in a solid gel. Custards are also cooked and served in the same container. So pecan pie and a pumpkin pie are... a...