[re-troh-rok-it] 
| 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. |
| ret·ro·rock·et (rět'rō-rŏk'ĭt) n. A rocket engine used to retard, arrest, or reverse the motion of a vehicle, such as an aircraft, missile, or spacecraft. |
troʊˌrɒk