What you call "powdered sugar" that you are used to - is it the kind that, if you mix it with a little water, it goes like cement and sets hard? So that you have to be careful not to get it damp? The kind of sugar that one uses to make frosting ("icing") on cakes? That is "icing sugar". There is another grade called "castor sugar" which is less powdery, half way between icing sugar and granulated sugar that goes in cups of tea, etc.