What does “Tourbillon” mean?

A tourbillon is a rotating cage that holds the escapement and balance wheel, the parts that regulate a mechanical watch's timekeeping. By turning continuously, usually once a minute, it averages out the effect of gravity on the balance in different positions. Abraham-Louis Breguet patented it in 1801, originally for pocket watches, which spend long periods in the same position.

In wristwatches, which change position constantly, the tourbillon's practical benefit to timekeeping is debated, but it remains a showcase of fine watchmaking and is usually displayed through an opening in the dial. Tourbillons are complex and expensive to service, so ask for the service history and confirm the cage rotates smoothly. Variations include the flying tourbillon, supported from one side only, and multi-axis tourbillons. Values vary enormously, from high-end manufacturers to more affordable makers, so the brand matters as much as the complication.

Example: 'Flying tourbillon, running well, last serviced by the brand.'