Maximum Tolerable Downtime (MTD)
The amount of time mission/business process can be disrupted without causing significant harm to the organization’s mission.
Source: NIST SP 800-34
Similar and Related to Maximum Allowable Downtime.
Maximum Tolerable Downtime (MTD) is the maximum amount of time a system can be down before it begins to cause significant disruption to operations. It is a measure of a system's availability and is used to determine the reliability of a system.