cas·ter sug·ar
noun/ˈkɑːstə ʃʊɡə(r)/
/ˈkæstər ʃʊɡər/
(also castor sugar)
[uncountable] (British English)- white sugar in the form of very fine grains, used in cooking
幼砂糖 Word Originmid 19th cent.: so named because it was suitable for use in a castor, a small container with holes in the top, used for sprinkling sugar.