back up

(noun) an accumulation caused by clogging or a stoppage. Synonyms: backup. 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, 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, backup, support.

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

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

(verb) give moral or psychological support, aid, or courage to. Synonyms: support, back up. Examples: "She supported him during the illness." "Her children always backed her up."

(verb) move backwards from a certain position. Synonyms: back up, back off, back down. Example: "The bully had to back down."

(verb) establish as valid or genuine. Synonyms: back, back up. Example: "Can you back up your claims?."

(verb) make a copy of (a computer file) especially for storage in another place as a security copy. Synonyms: back up. Example: "You'd better back up these files!."

(verb) become or cause to become obstructed. Synonyms: clog, choke off, clog up, back up, congest, choke, foul. Examples: "The leaves clog our drains in the fall." "The water pipe is backed up."