Today Cabriolet describes open top cars derived from a sedan or coupe. It could also be understood to mean an open top car with two rows of seats with just two doors. Although in reality it can have any number of doors and windows. In England from 1920 and up, a chummy was an open top car. It is however applied today by owners of almost any collectible car more that is more than 25 years old.
Modern equivalent is the pinstripe.
In the US from 1927 on, the term was used to mean a car with a soft, retractable top was hooked permanently to the bodywork, and therefore not removable like a roadster's was. Other requisites were side windows that opened and the absence of any framework above the waist of the car apart from the windshield. The most common example of the was therefore called a convertible coupe these had two doors, whilst cars with four doors were called convertible sedans. In both cases four or five people could be seated. Used by Lincoln, Chrysler and others about 1930 to emphasize sportiness.