n. - The strap of a bridle, fastened to the curb or snaffle on each side, by which the rider or driver governs the horse.
n. - Hence, an instrument or means of curbing, restraining, or governing; government; restraint.
v. t. - To govern or direct with the reins; as, to rein a horse one way or another.
v. t. - To restrain; to control; to check.
v. i. - To be guided by reins.