retrorocket /ˈrɛtrəʊˌrɒkɪt/

• 1. 

  N 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 大型火箭、导弹或航天器上的备用发动机; 产生和航线反方向的猛推，以使其减速或向后退 (Often shortened to retro)