I think its any form of human powered wheeled vehicle. Its just dawned on me too that its from where the Velodrome as a cycling venue got its name. Which then led me to a brainwave for a new Olympic sport - put some rails in and race a few laps of those railway velocipedes. You could have different classes depending on the number of wheels and whether hand or foot pedal operated.
Back to sleep and the land of dreams now....
Hi, Velodrome I believe comes from the French word of Velo for bicycle. Also this applies to Velocipedes as the velo means bicycle in French.