Flaky dough / crust is a general way of describing light, 'flaky', crumbly crusts, that are usually used in dessert (primarily pie) recipes. The flour-based dough is mixed, albeit lightly, with either butter or shortening, until ingredients are combined, but still heterogeneous (you should be able to see little bits of unblended butter / shortening in the mixture). The flour surrounding these little bits of butter / shortening will get 'puffed' up when the butter gets hot and the water in the melting butter evaporates into steam. This separates the flour dough into spaced layers that make for a flaky, light, 'tasty' crust!
--- see picture for an idea! ---
Hope that helps ; )