The glaze on a doughnut is the thin sweet coating that makes your fingers sticky. The glaze on a coffee table is the shiny coating that makes it glossy. The glaze on your friend's eyes as you talk is a sign that maybe you're boring her.
Like glass, a glaze is a shiny clear substance so it's no surprise that they both come from the same root word glas. Objects that have a glaze on them include ceramic pots and doughnuts. If you glaze over something, you're covering it with a thin clear substance that makes it look polished. If someone says your eyes are starting to glaze over, snap out of it and look alive.