WordNet (r) 3.0 (2006):
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, rein in] 2: control and direct with or as if by reins; "rein a horse" [syn: harness, rein in, 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, rein in]