Rein \Rein\, v. t. [imp. & p. p. {Reined} (r?nd); p. pr. & vb. n. {Reining}.] 1. To govern or direct with the reins; as, to rein a horse one way or another. He mounts and reins his horse. --Chapman. 2. To restrain; to control; to check. Being once chafed, he can not Be reined again to temperance. --Shak. {To rein in} or {rein up}, to check the speed of, or cause to stop, by drawing the reins.