Waffle fries are a type of french fry that are lattice-shaped. They're created by cutting the potato using a mandoline, wave slicer, or similar cutting device featuring a wavy/waffle blade. After slicing the potato one way, the potato is quarter-turned and sliced again, thus producing the crisscross shape of the fries.
The fast food chain Chick-Fil-A is noted for selling waffle fries.