Hot rods are typically American cars with large engines modified for linear speed. The origin of the term "hot rod" is unclear. One explanation is that the term is a contraction of "hot roadster," meaning a roadster that was modified for speed. Another possible origin includes modifications to or replacement of the camshaft(s), sometimes known as a "stick" or "rod". A camshaft designed to produce more power is sometimes call a "hot stick" or, here, a "hot rod". Roadsters were the cars of choice because they were light. The term became commonplace in the 1930s or 1940s as the name of a car that had been "hopped up" by modifying the engine in various ways to achieve higher performance.

The term can also apply to other items that are "souped up" for a particular purpose, such as "hot-rodded amplifier".