"As backup" is a phrase that refers to having a secondary plan, resource or person available in case of unforeseen circumstances. There are many synonyms that can be used to express this concept, such as "safety net", "contingency plan", "backup plan", "fallback option", "reserve", "spare", "alternate", "substitute", "standby", "emergency plan" and "support system". Using these synonyms provides a diverse range of options that allow for flexibility in communication and can help to emphasize the importance of preparing for unexpected events. Regardless of the words used, having a backup plan is crucial for success in any endeavor.