a small, auxiliary rocket engine, forming a part of a larger rocket vehicle and having its exhaust nozzle pointed toward the direction of flight, for decelerating the larger rocket, separating one stage from another, etc.
The bottom unit consisted essentially of four landing struts equipped with a retrorocket to cushion the descent.
They could have saved themselves loads of grief by including a small, solid-fuel retrorocket in the satellite design.
British Dictionary definitions for retrorocket
a small auxiliary rocket engine on a larger rocket, missile, or spacecraft, that produces thrust in the opposite direction to the direction of flight in order to decelerate the vehicle or make it move backwards Often shortened to retro