noun
cleansing powder; washing powder
Dated term for a powdered cleanser used for washing hair, skin, or tableware. Modern equivalents are often liquid or cream cleansers.
祖母は昔、洗い粉で髪を洗っていた。
My grandmother used to wash her hair with cleansing powder.
洗剤 is the general modern term for detergent or cleanser, while 洗い粉 specifically refers to an older powdered form.
Compound of 洗い (arai, 'washing', the continuative form of 洗う) and 粉 (ko, 'powder').