n.1 part of a scene, picture, or description, that serves as a setting to the chief figures or objects and foreground.
2 an inconspicuous or obscure position (kept in the background).
3 a person's education, knowledge, or social circumstances.
4 explanatory or contributory information or circumstances.
5 Physics low-intensity ambient radiation from radioisotopes present in the natural environment.
6 Electronics unwanted signals, such as noise in the reception or recording of sound.
Phrases and idioms:
background music music intended as an unobtrusive accompaniment to some activity, or to provide atmosphere in a film etc.