Preheat waffle iron to medium and spray with nonstick cooking spray.
In a large bowl, whisk together flour, baking powder, sugar, cinnamon, nutmeg and salt until just combined. Add melted butter, eggnog, egg, and vanilla extract. Mix until incorporated.
Scoop batter by 1/2 cupfuls (or more for larger waffles) onto heated waffle iron and cook according to manufacturer's directions, until waffles are brown and crispy.
Eggnog Glaze:
In small bowl or measuring cup mix together powdered sugar and eggnog until smooth and glaze-like texture.
If glaze is too thin, add more powdered sugar; too thick, add more egg nog.
Drizzle on hot waffles and serve immediately.
Notes
To keep waffles crispy in between cooking, place on wire baking rack to cool.