WordNet
n. the ratio of the drag on a body moving through air to the product of the velocity and the surface area of the body [syn: coefficient of drag]
Wikipedia
In fluid dynamics, the drag coefficient (commonly denoted as: $\scriptstyle C_\mathrm d\,$, $\scriptstyle C_\mathrm x\,$ or $\scriptstyle C_\mathrm w\,$) is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment, such as air or water. It is used in the drag equation in which a lower drag coefficient indicates the object will have less aerodynamic or hydrodynamic drag. The drag coefficient is always associated with a particular surface area.
The drag coefficient of any object comprises the effects of the two basic contributors to fluid dynamic drag: skin friction and form drag. The drag coefficient of a lifting airfoil or hydrofoil also includes the effects of lift-induced drag. The drag coefficient of a complete structure such as an aircraft also includes the effects of interference drag.
Usage examples of "drag coefficient".
He sank back and let his hands trim flaps and ailerons, clearing up the drag coefficient until the plane was flying smoothly and lifting well.
The sculptured body kit improved the car's drag coefficient significantly, while the lowered and stiffened suspension, allied to a set of Metzler ultra-high performance tires, gave the car superior handling and cornering capabilities.