Originally, the lead sled referred to extensively repaired/modified cars due to the use of lead as body filler and was, for the most part, an insult.

Since the introduction of artificial fillers (such as Bondo), the term has come to mean a post-war, large (full size) American car of the 1950s.

A lead sled tends to have all extra side moldings shaved off and filled with the suspension lowered. Lead sleds are built for style, not speed. Some common lead sleds are the 1949 Mercury, 1949 Ford and the 1959 Cadillac.

Aircraft nicknames - It has also been used as a nickname for a variety of US military aircraft, including the F3H Demon, F-84 Thunderjet, F-105 Thunderchief, and SR-71 Blackbird.

The Auto Channel - Car Speak-To-English Glossary of Terms

Lead ( /ˈlɛd/) is a main-group element in the carbon group with the symbol Pb (from Latin: plumbum) and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed to air. Lead has a shiny chrome-silver luster when it is melted into a liquid.

Lead is used in building construction, lead-acid batteries, bullets and shots, weights, as part of solders, pewters, fusible alloys and as a radiation shield. Lead has the highest atomic number of all of the stable elements, although the next higher element, bismuth, has a half-life that is so long (much longer than the age of the universe) that it can be considered stable. Its four stable isotopes have 82 protons, a magic number in the nuclear shell model of atomic nuclei.

Lead, at certain exposure levels, is a poisonous substance to animals as well as for human beings. It damages the nervous system and causes brain disorders. Excessive lead also causes blood disorders in mammals. Like the element mercury, another heavy metal, lead is a neurotoxin that accumulates both in soft tissues and the bones. Lead poisoning has been documented from ancient Rome, ancient Greece, and ancient China.

A sled, sledge, or sleigh is a land vehicle with a smooth underside or possessing a separate body supported by two or more smooth, relatively narrow, longitudinal runners that travels by sliding across a surface. Most sleds are used on surfaces with low friction, such as snow or ice. In some cases, sleds may be used on mud, grass, or even smooth stones. They may be used to transport passengers, cargo, or both. Shades of meaning differentiating the three terms often reflect regional variations depending on historical uses and prevailing climate.

In Britain the three terms are generally quite similar in meaning, although sledge usually refers to a smaller sled, used mostly for freight, one that can generally transport no more than one or two persons with only a limited amount of cargo. Sledges may be pulled by dogs or other smaller animals, although confusingly a sledge pulled by a dog in British English is often referred to as a dog-sled. A small recreational sled, pulled by humans, can also be referred to as a sledge.Sleigh (pronounced "slay") remains largely a synonym for sled regardless of its capacity (and similarly in Canada).