In a large bowl, whisk together the flour, sugar, baking powder, baking soda, salt, cinnamon, ginger, and nutmeg.
In a separate bowl, whisk together the sourdough discard, milk, pumpkin purée, egg, oil, and vanilla until smooth.
Pour the wet ingredients into the dry ingredients and stir until just combined. Some lumps are fine! Let the batter rest for 10 - 15 minutes while your waffle iron preheats.
Heat your waffle maker according to the manufacturer’s instructions. Lightly grease with nonstick spray.
Pour the batter into the hot waffle iron. Cook until golden brown and crisp.
Serve warm with your favorite toppings. Freeze leftovers in a single layer, then store in an airtight container or freezer bag.