The phrase "smooth sauce" refers to a sauce that has a silky, consistent texture without any lumps or chunks. It means that the sauce is well-blended and has a nice, even consistency. Full definition
With blender motor running, add olive oil in steady stream until smooth sauce forms. (vegetariantimes.com)
For peanut sauce, blend all ingredients in a blender until smooth sauce. (jaxhouse.com)
I use pizza sauce because it is the lowest carb tomato sauce I can find and my husband much prefers smooth sauces to chunky ones. (edesiasnotebook.com)