What is the definition of a roadster vehicle?

What is the definition of a roadster vehicle?
(new edit) in the strictest sense this may have been true once. however, in common usage today any front engined, rear drive, convertible, with an emphasis on handling rather than horsepower would be considered a roadster. For example the Mazda MX-5 Miata is the quintessential modern roadster.

the term roadster was also applied to racing cars in 1950's America where the engine and drive shaft were offset from the centerline of the car allowing the driver to sit lower in the car which improved handling on the oval tracks of the day. the practice was eventually discontinued when rear engined race cars became dominant.

so, the term "roadster" for all practical purposes has been applied to so many different types of cars over the years it has lost much of its meaning. if you ask 5 different gear heads you will probably get 5 different "right" answers.