Aerophones of conical bore with a widely flared bell, funnel-shaped mouthpiece, and slender tube which curves into wide circular coils; today it is furnished with valves, which are usually positioned to be played by the left hand while the right hand is placed in the bell for stopping. Commonly used in the brass section of Western-style orchestras as well as smaller ensembles and in solo work.

Source: Art & Architecture Thesaurus

http://vocab.getty.edu/page/aat/300042319