frost·ing / ˈfrôsting/ • n. 1. icing.2. a roughened matte finish on otherwise shiny material such as glass or steel.

frosting
1. American name for icing on cakes; in the UK icing made from sugar and egg white (known as American or royal icing).

2. A way of decorating the rim of a glass in which a cold drink is to be served; the edge is coated with whipped egg white, dipped into caster sugar, and allowed to dry.

3. For a margarita cocktail the edge of the glass is frosted by dipping it into lemon juice, then salt.