Something with a glossy, shiny surface is glazed. Your favorite doughnuts might be glazed with icing, and your least favorite kind of road to drive on could be glazed with ice after a winter storm.
Glazed pottery is coated with a smooth and gleaming layer. You can also use the adjective glazed to describe a person's emotionless or glassy eyes, or windows that are fitted with panes of glass. All of these meanings come from the verb glaze, a variation on the Middle English glasen, which means both "to fit with glass" and "to make shine."