From SKYbrary Wiki
On many variable pitch propellers, the blade pitch can be increased to the point that the chord line of the blade is approximately parallel to the on-coming airflow. This process is referred to as feathering.
The inflight feathering of the propeller, on an engine that has failed or has been intentionally shut down, greatly reduces the drag that would occur with the blade pitch in any other position. On a single engine aircraft such as a motor glider, feathering the propeller when the engine is shut down results in a significant increase in gliding distance. On a multi-engine aircraft, feathering the propeller of a failed engine results in both a reduction in drag and a reduction in adverse yaw vastly improving the engine-out handling characteristics and the engine-out flight performance of the aircraft.