Glider

[Monty]

A very light aircraft, also called [sailplane] without engine thrust. It needs to be lifted up by a small prop aircraft. Once it is at a sufficent [altitude], the cable used for lifting up is detached from its nose and the glider flies freely. In order to maintain its altitude, glider pilots use to catch the so called lifting or [ascending] windstreams, usually generated by hot air moving up to clouds, and mountainous landscapes.

2)Usually told about an aircraft who has lost any thrust because of engine failure or running out of fuel.

[Dave Paprocki]

A light aircraft that is designed to fly without using an engine.

[Sarah]

an aircraft that has long fixed wings and no engine and flies by gliding