derating

This term is defined in ECSS-S-ST-00-01C as
action when designing a product to limit the component stresses to specified levels that are below their ratings in order to increase its reliability

This term is defined in ECSS-Q-ST-30-11C Rev.1 as
process of designing a product such that its components operate at a significantly reduced level of stress to increase reliability and to insure useful life and design margins