Source : WordNet®

rein in
     v 1: 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" [syn: {rein}]
     2: control and direct with or as if by reins; "rein a horse"
        [syn: {harness}, {draw rein}, {rein}]
     3: stop or check by or as if by a pull at the reins; "He reined
        in his horses in front of the post office" [syn: {rein}]