Plain English Meaning
A spinning gyro that holds whatever direction it was set to, with nothing automatically keeping it aligned. The pilot has to reset it every so often because it slowly drifts off.
Full Definition
A gyroscope that is not slaved or corrected to any external reference such as the Earth's magnetic field. Once spun up and set, it holds its position in space and any indication it provides drifts over time as the Earth rotates and as small mechanical errors accumulate, requiring periodic manual realignment by the pilot.
Context Anchor
Seen in remote indicating compass systems when the heading indicator is operated without automatic correction from the ’s .