Plain English Meaning
It is a flight control setup where the autopilot, flight director, and navigation aids are built to work together as one connected system instead of as separate pieces.
Full Definition
An integrated flight control system is a single combined system that brings together the autopilot, flight director, and related navigation and attitude functions so they work together as one unit. The pilot interacts with one set of controls and one display logic, rather than operating each subsystem separately.
Context Anchor
Seen in instrument flying when using systems such as a flight director, autopilot, navigation display, and mode controls together rather than as separate pieces of equipment.