The double bass is the largest and lowest of the orchestra’s string instruments. It has generally four or five strings and its music sounds an octave (eight notes) lower than it is written. If, as often in music before 1800, the double bass plays the same music as the cello, the sound will be an octave lower.

large musical instrument in the string family.

The bass member of the violin family. The double bass differs from the rest of the instruments in its family in that it is a descendant of the viola da gamba family  rather than of the viola da bracci [..]

the use of two bass drums with a drum set. Double bass drumming can also be played with a twin or double bass pedal and just one bass drum.

(music) The largest stringed instrument of the violin family. The deepest of all male voices. ''Voice of a double bass, or simply, a double bass.''