backup

(noun) an accumulation caused by clogging or a stoppage. Examples: "A traffic backup on the main street." "He discovered a backup in the toilet."

(noun) someone who takes the place of another (as when things get dangerous or difficult). Synonyms: stand-in, substitute, relief, reliever, backup man, fill-in. Examples: "The star had a stand-in for dangerous scenes." "We need extra employees for summer fill-ins."

(noun) a musical part (vocal or instrumental) that supports or provides background for other musical parts. Synonyms: accompaniment, musical accompaniment, support.

(noun) (computer science) a copy of a file or directory on a separate storage device. Synonyms: computer backup. Examples: "He made a backup in case the original was accidentally damaged or erased."

(noun) the act of providing approval and support. Synonyms: backing, championship, patronage. Examples: "His vigorous backing of the conservatives got him in trouble with progressives."