rein in in WordNet English dictionary

1. control and direct with or as if by reins
   "rein a horse"
   harness  rein in  draw rein  rein 
   
2. 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"
   rein  rein in 
   
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"
   rein  rein in 
   

rein in in English Wiktionary