Final answer:
The average percentage of time that servers are busy providing service to customers is referred to as server duty cycle.
Step-by-step explanation:
The average percentage of time that servers are busy providing service to customers is referred to as server duty cycle. The duty cycle represents the proportion of time that a server spends actively engaged in serving customers. For example, if a server is active for 40% of the time, then its duty cycle is 40%. This concept is commonly used in computer networks and telecommunications.