From Longman Dictionary of Contemporary Englishdouble bassdouble bass /ˌdʌbəl ˈbeɪs/ (also bass) noun [countable] APMa very large musical instrument shaped like a violin that the musician plays standing up
Examples from the Corpus
double bass• This is even more pronounced on a double bass which has even lower-pitched notes.• I met him at a dance, a nice soldier who was playing double bass in the band.• He wrote prolifically for the double bass, as well as for other solo instruments and ensembles.• The normal layout of the string orchestra is in four-part harmony, the double bass either doubling the cellos or being silent.• Then I took up the double bass and organ for good measure. 