A rat rod, as usually known today, is a custom car with a deliberately worn-down, unfinished appearance, typically lacking paint, showing rust, and made from cheap or cast-off parts. These parts can include non-automotive items that have been repurposed, such as a rifle used as a gear shifter, wrenches as door handles, or hand saws as sun visors. Whether or not so appointed, the rat rod uniquely conveys its builder’s imagination.

Hot rods are typically American cars that might be old, classic, or modern and that have been rebuilt or modified with large engines optimized for speed and acceleration. One definition is: "a car that's been stripped down, souped up and made to go much faster." However, there is no definition of the term that is universally accepted and the term is attached to a wide range of vehicles. Most often they are individually designed and constructed using components from many makes of old or new cars, and are most prevalent in the United States and Canada. Many are intended for exhibition rather than for racing or everyday driving.