superfine sugar       
noun [ U ] US uk/ˌsuː.pə.faɪn ˈʃʊɡ.ər/ us/ˌsuː.pɚ.faɪn ˈʃʊɡ.ɚ/ (UK caster sugar)
 (经常用于烹饪)超细白糖
white sugar with very small grains, often used in cooking
  Add in the superfine sugar and continue to whip to stiff peaks.
 He made a caramel sauce out of butter, superfine sugar, and whipping cream.
 Compare: brown sugarconfectioner's sugardemerara sugargranulatedicing sugarpowdered sugar
 - More examples
 - Gradually beat in half a cup of superfine sugar.
 - Superfine sugar resembles sand in an hourglass.
 - Superfine sugar should not be confused with confectioner's sugar, which is sugar crushed into a fine powder.