The rhythm section of a band is the musicians whose main job is to supply the rhythm. It usually consists of bass and drums, and sometimes keyboard instruments.
rhythm section in British English
noun
those instruments in a band or group (usually piano, double bass, and drums) whose prime function is to supply the rhythm
rhythm section in American English
those instruments in a band, as the drums, bass viol, etc., that mainly supply rhythm
Examples of 'rhythm section' in a sentence
rhythm section
The lungs and the heart, the bass and the drums, the rhythm section.