(1):

(n.) Ground in the rear or behind, or in the distance, as opposed to the foreground, or the ground in front.

(2):

(n.) Anything behind, serving as a foil; as, the statue had a background of red hangings.

(3):

(n.) The space which is behind and subordinate to a portrait or group of figures.

(4):

(n.) A place in obscurity or retirement, or out of sight.