throttle (something) back/down
phrasal verb with throttle verb [ T ] uk/ˈθrɒt.əl/ us/ˈθrɑː.t̬əl/
（调节油门）减速
to reduce speed, or to reduce the power and speed being produced by an engine
The pilot throttled back (the engines) as he came in to land. 着陆时，飞行员调节油门减速。