vi to be guided by reins.
2. rein ·vt to govern or direct with the reins; as, to rein a horse one way or another.
3. rein ·noun hence, an instrument or means of curbing, restraining, or governing; government; restraint.
4. rein ·vt to restrain; to control; to check.
5. rein ·noun the strap of a bridle, fastened to the curb or snaffle on each side, by which the rider or driver governs the horse.