n.

1. 韁繩[C][P1]
   Pull on the right rein and the horse will turn to the right.

   一拉右韁，馬就會向右轉。

2. 駕馭，控制，統治[P1]
   Few kings now hold the reins of government.

   現在很少有國王是掌握政權的。

vt.

1. （用韁繩）勒住[（+in/back/up）]
   The officer reined in his horse at a crossroads.

   軍官在十字路口勒住了馬。

2. 駕馭；控制，統治[O][（+in）]
   You must learn to rein in your temper.

   你必須學會控制你的脾氣。

vi.

1. 勒馬，勒住牲口[（+back/in/up）]
   He reined in as he approached the busy road.

   他在靠近繁忙的公路時勒馬緩行。

n.

1. a long, narrow strap attached at one end to a horse's bit, typically used in pairs to guide or check a horse in riding or driving.
   ▸Brit. a pair of straps used to restrain a young child.
2. (reins) the power to direct and control:
   a new manager will soon take over the reins.

v.

1. check or guide (a horse) by pulling on its reins.
2. (often rein someone/thing in/back) restrain.