"Powder detergent" refers to a type of cleaning product that comes in a dry, fine form. It is used to clean clothes or dishes by dissolving in water to create a soapy solution. Full definition
A cup of powdered detergent will dissolve in water and can wash away that stain in your clothing. (giantmommy.com)
If you don't use liquid, then be careful about what kind of powdered detergent you buy. (treehugger.com)
It's easy to measure out powder detergents such as Nellies, but if you are using liquid detergent such as Allens Naturally, consider putting it into a hand - soap dispenser. (thinking-about-cloth-diapers.com)