This term is defined in ECSS-E-ST-10-11C as
set of instructions available to the users for system and payload execution that describe the specific sequence of operations to be performed by the users to logically, safely, and efficiently accomplish nominal and off nominal tasks during the mission

This term is defined in ECSS-E-ST-70-32C as
means for interacting with the space system in order to achieve a given objective or sequence of objectives

This term is defined in ECSS-S-ST-00-01C as
documented way to carry out an activity or process in a controlled manner