Maximum Cross Section

for a body moving through water or air (for example, a torpedo, the hull of a ship, or the fuselage of an airplane or rocket), the cross section of the body with the largest area in a plane perpendicular to the direction of motion. The force of drag acting on the body is usually related to the maximum cross section. The area of the maximum cross section is also taken to mean the area of the body’s projection onto a plane perpendicular to the direction of its motion.