retrorocket
noun [ C ] uk/ˌret.rəʊˈrɒk.ɪt/ us/ˌret.rəˈrɑː.kɪt/
反推进火箭;制动火箭（宇宙飞船或航空飞机等航空器上的一种火箭，其发射方向与航空器飞行方向相反，从而使之减速）
a rocket on a spacecraft or an aircraft that fires in the opposite direction to the direction in which the vehicle is travelling, in order to slow it down