Plain English Meaning

People learning to fly gliders — aircraft without engines that stay up by riding rising air. They are mentioned as an example of students who benefit from picturing maneuvers in their head before flying them.

Full Definition

Student pilots training to fly gliders — engineless aircraft that stay airborne by using rising air currents and efficient aerodynamic design rather than engine thrust. In the Aviation Instructor's Handbook, this group is referenced when discussing how visualization techniques are used during instruction, since glider students must mentally rehearse flight maneuvers, energy management, and landing approaches before performing them in an aircraft that cannot simply add power to recover.