The phrase "cornmeal mixture" refers to a combination of cornmeal with other ingredients, usually liquid such as water or milk, to create a mixture or batter. Full definition
Working in batches, dredge fish in cornstarch, shaking off excess, then coat with egg, allowing excess to drip back into bowl, then coat with cornmeal mixture, pressing to adhere and shaking off excess, and transfer to a plate. (epicurious.com)
Stir onion into cornmeal mixture, then fold in egg mixture. (vegetariantimes.com)
Add cornmeal mixture to boiling water, stirring constantly. (health.com)