Definition of 'tuba'

a bowed stringed instrument, the highest member of the violin family, consisting of a fingerboard, a hollow wooden body with waisted sides, and a sounding board connected to the back by means of a soundpost that also supports the bridge. It has two f-shaped sound holes cut in the belly. The instrument, noted for its fine and flexible tone, is the most important of the stringed instruments. It is held under the chin when played. Range: roughly three and a half octaves upwards from G below middle C

a keyed woodwind instrument with a cylindrical bore and a single reed. It is a transposing instrument, most commonly pitched in A or B flat

a keyboard percussion instrument consisting of a set of steel plates of graduated length that are struck with key-operated hammers. The tone is an ethereal tinkling sound. Range: four octaves upwards from middle C

a large shallow drum of low and indefinite pitch

the largest instrument in the oboe family, pitched an octave below the bassoon; double bassoon