1. Auxiliary
2. Spare
3. Reserve
4. Secondary
5. Duplicate
6. Backup copy
7. Replica
8. Reinforcement
9. Standby
10. Reserve copy
11. Contingency
12. Reinstate
13. Redundancy
14. Safeguard
15. Reserve supply
16. Alternate
17. Support
18. Back-up
19. Reserve stock
20. Repetition
21. Subsidiary
22. Reserve force
23. Reserve system
24. Fallback
25. Reserve plan
26. Reinstatement
27. Duplication
28. Replacement
29. Reserve unit
30. Reserve fund

When it comes to having a backup plan, there are many words that can be used to describe it. Synonyms for the term “backup” include auxiliary, spare, reserve, secondary, duplicate, backup copy, replica, reinforcement, standby, reserve copy, contingency, redundancy, safeguard, reserve supply, alternate, support, back-up, reserve stock, repetition, subsidiary, reserve force, reserve system, fallback, reserve plan, reinstatement, duplication, replacement, reserve unit, and reserve fund. These words can be used to describe a backup plan, ensuring that you have the best ideas in place in case of an emergency. Whether you are looking for another word for backup, other words for backup, or the best ideas for a backup plan, these synonyms are sure to help.