The state of a trunk group when all trunks are in use. The trunk group cannot accept any new inbound or outbound calls in this state. The ICR tracks the amount of time during which all trunks in a trunk group are busy. You can view this information in real-time or historical reports.

Condition in which all trunks in a group are engaged.

When all trunks are busy in a specified trunk group. Generally, reports indicate how many times all trunks were busy, and how much total time all trunks were busy; unfortunately, it does not indicate how many customers received a busy signal. Experience would give you a reasonable idea though.