The term for a hybrid environment that normally uses a private cloud to run critical applications but will use public cloud services to meet spikes in resource usage is Hybrid Cloud Bursting.
In a hybrid cloud bursting scenario, organizations maintain their core infrastructure and sensitive data in a private cloud for security and control.
But when there is a sudden increase in demand for computing resources, such as during seasonal peaks or unexpected surges in workload, the organization can seamlessly leverage the scalability of the public cloud to meet these demands.
This approach provides flexibility and cost-effectiveness while ensuring the availability and performance of critical applications.