"Dry mustard" refers to a powdered form of mustard that does not have any liquid or vinegar added to it. It is used as a spice in cooking to add a strong, spicy flavor to dishes. Full definition
I added a generous 1/4 tsp dry mustard to the sauce (because I really like mustard and sausage together) and used fresh mozzarella. (smittenkitchen.com)
Mix the salt, pepper, cayenne pepper, garlic powder, onion powder and dry mustard powder together in a bowl. (cookingchanneltv.com)
Mix the soy sauce, honey, vegetable oil, and dry mustard in a bowl, then pour it into the bag. (fieryfoodscentral.com)