Dictionary definition · rein in
verb
- 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"
- control and direct with or as if by reins"rein a horse"
- stop or check by or as if by a pull at the reins"He reined in his horses in front of the post office"
Source: Open English WordNet (CC BY 4.0).