a crumbly topping, as for coffeecake, made with flour, butter, sugar, and cinnamon
See streusel in American Heritage Dictionary 4
streu·sel
noun
A crumblike topping for coffee cakes and rich breads, consisting of flour, sugar, butter, cinnamon, and sometimes chopped nutmeats.
Origin: German, streusel, from Middle High German ströusel, something strewn, from ströuwen, to sprinkle, from Old High German strowwen; see ster-2 in Indo-European roots.