frosting

(frôˈstĭng, frŏsˈtĭng)

noun

1. Icing, as on a cake.
2. A roughened or speckled surface imparted to glass or metal.

Regional Note: Although both frosting and icing are widespread, people in New England, the Upper Midwest, and the Western U.S. tend to put frosting on cake. In Pennsylvania, New Jersey, the Lower Midwest, and all of the South, the preferred term is icing. There is some overlap, especially in upstate New York, Michigan, and California, but the regions in which the two words predominate are surprisingly distinct. A few people in the South call it by a third name, filling, even when it goes on top.