1. In cooking, to dust a preparation (such as a cake or bread) involves lightly coating it with a powdery ingredient such as flour, powdered sugar or cocoa powder. The sugar, cocoa, etc., is typically placed in a fine sieve, then the strainer is tapped or shaken lightly to release a fine dusting of the ingredient. The dusting adds both flavor and visual effect. 2. The word "dust" is also used to describe inferior, coarsely crushed tea leaves.
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.