Noun
(comedy) A circus clown routine in which an implausibly large number of clowns climb into or out of a small car.
The undersized car used in a circus clown car routine.
(by extension) A very small car.
(by extension) A car or small enclosed space with too many people in it.
(figuratively, usually derogatory) Any process with a comically large number of participants.
A car that looks gaudy or otherwise ridiculous.
A car for clowns, especially the car of a circus train that carries the clowns.
Source: en.wiktionary.org