spoiler

A spoiler is an  automotive aerodynamic  device whose intended design function is to 'spoil' unfavorable air movement across a body of a vehicle in motion, usually described as turbulence or drag. Spoilers on the front of a vehicle are often called air dams, because in addition to directing air flow they also reduce the amount of air flowing underneath the vehicle which generally reduces aerodynamic lift and drag. Spoilers are often fitted to race and high-performance sporty cars,although they have become common on passenger vehicles as well. Some spoilers are added to cars primarily for styling purposes and have either little aerodynamic benefit or even make the aerodynamics worse.

The term "spoiler" is often mistakenly used interchangeably with "wing". An automotive wing is a special type of spoiler whose intended design is to generate down force as air passes around it, not simply disrupt existing airflow patterns. As such, rather than decreasing drag wings actually increase drag.