Rein Very Common

one of a pair of long straps (usually connected to the bit or the headpiece) used to control a horse

"The rider tightened his reins as he guided the horse around the tight turn."

any means of control

"he took up the reins of government"

A strap or rope attached to a bridle or bit, used to control a horse, animal or young child.

"The old anatomical text warned that cutting into the wrong part of the flank could damage a rein and cause severe internal bleeding."

A kidney.

control and direct with or as if by reins

"rein a horse"

stop or slow up one's horse or oneself by or as if by pulling the reins

"They reined in in front of the post office"

stop or check by or as if by a pull at the reins

"He reined in his horses in front of the post office"

keep in check

"rule one's temper"

To direct or stop a horse by using reins.

"The rider gently pulled on the reins to guide the mare around the tight turn in the corral."

A surname, from German​.

"The judge asked if Mr. Rein could clarify his statement before ruling on the case."