Cylinder/ˈsɪlɪndər/ Definition 1 of 4Pro Tip 1/3Geometric Form A cylinder in geometry is shaped with two identical circles connected by a surface. Can you draw a cylinder next to the cube? Pro Tip 2/3Everyday Objects Many everyday items are cylindrical, making it a familiar shape to recognize. The paper towel roll is a perfect example of a cylinder. Pro Tip 3/3Not Always Solid Cylinders can be hollow, like a tube, or solid, like a metal rod. The cardboard core of the wrap is a hollow cylinder.