splits along a ray in a piece of timber. They do not usually affect the strength of the material but can cause distortion, particularly if the timber suddenly becomes wet. Cup shakes are splits separating the annual rings.
Wood shingles. Usually cedar thay are used for roofing and siding.
what daddy gets when the booze runs low...or a type of wood (usually cedar) shingle. Like a shingle, except less well formed and usually larger. Shakes will come in bundles of varying sizes and it is up the roofer to fit them together in such a way that is not offensive to the neighbors.