Dictionary definition · rein
noun
- one of a pair of long straps (usually connected to the bit or the headpiece) used to control a horse
- any means of control"he took up the reins of government"
verb
- control and direct with or as if by reins"rein a horse"
- 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"
- stop or check by or as if by a pull at the reins"He reined in his horses in front of the post office"
- keep in check"rule one's temper"
Source: Open English WordNet (CC BY 4.0).