powdered sugar UK /ˈpaʊ.dəd ˈʃʊɡ.ə/US /ˈpaʊ.dɚd ˈʃʊɡ.ɚ/ noun1 •(US) Very finely ground sugar to which cornstarch is added to prevent lumping, mostly used in icings and confections to produce a smooth texture. formspowdered sugars