Plain English Meaning
The way the inner frame holding a spinning gyro tilts on its pivot. That tilt is what the instrument measures and shows on the dial.
Full Definition
The movement of a gyroscope's supporting frame (the gimbal) about its pivot axis, allowing the spinning gyro rotor to maintain its orientation in space while the instrument case and aircraft move around it. In the turn coordinator, the gimbal is canted about 30 degrees from the longitudinal axis, so its rotation responds to both roll and yaw, driving the miniature aircraft .