Rigatoni are a form of tube-shaped pasta of varying lengths and diameters. They are larger than penne and ziti, and sometimes slightly curved, though nowhere near as curved as elbow macaroni. Rigatoni characteristically have ridges down their length, sometimes spiraling around the tube. And unlike penne, rigatoni's ends are cut square to the tube walls instead of diagonally.
The word rigatoni comes from the Italian word rigato, which means "ridged" or "lined", and is associated with the cuisine of southern and central Italy. Rigatoncini are a smaller version, close to the size of penne. Their name takes on the diminutive suffix -ino denoting their relative size.
Rigatoni is a particular favorite pasta shape in the south of Italy, especially in Sicily. Its namesake ridges make better adhesive surfaces for sauces and grated cheese than smooth-sided pasta like ziti.