backupone who supports or reinforces another: I?m his backup; (computers) a copy or duplicate version of a file, program, or computer system: I made a backup of the file.Not to be confused with:back up ? to support someone?s opinion or order: I back up his no-smoking rule.; to move backward: Back up and give him some air!Abused, Confused, & Misused Words by Mary Embree Copyright © 2007, 2013 by Mary Embreeback·up (b?k??p?)n.1. a. A reserve or substitute.b. Computers A copy of a program or file that is stored separately from the original.2. a. Support or backing.b. Music A background accompaniment, as for a performer.3. An overflow or accumulation caused by clogging or by a stoppage: a backup in the sink; a backup of traffic at the drawbridge.adj. Extra; standby: a backup pilot.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.back?up (?bæk??p) n. 1. one that supports or reinforces, as a group of musicians supporting a soloist. 2. an accumulation due to stoppage. 3. an alternate or substitute kept in reserve. 4. a. a copy of a computer file or program kept in case the original is damaged or lost. b. a procedure to follow in such an event. [1775?85, Amer.] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.backupA copy made of important data and kept in case something goes wrong with the original.Dictionary of Unfamiliar Words by Diagram Group Copyright © 2008 by Diagram Visual Information Limited