noun
backup
BAK-uhp
noun
1
A person, plan, or system kept in reserve in case the main one fails.
"Always bring a backup charger when you travel."
"The understudy served as backup in case the lead actress got sick."
2
A copy of digital files kept separately so the originals can be restored if lost or damaged.
"She lost her laptop, but luckily she had a backup of all her photos in the cloud."
3
A buildup or blockage that stops something from flowing normally, such as traffic or plumbing.
"There was a serious backup on the highway after the accident."
How to Use Backup
Learner’s notesIn plain EnglishSomething held in reserve for support, or a saved copy of data, or a jam that stops normal flow.
Common pairings
backup plan
backup files
traffic backup
call for backup
Word Forms
backups plural
Study it as flashcards or scroll it in Flow — saved to your collection.
Test yourself on “backup”
A quick quiz — meaning, synonyms & usage
→
Fill the Gap
Can you complete this real example?
Always bring a _____ charger when you travel.
Etymology
A noun formed from the phrasal verb back up, meaning to support or reinforce from behind.