The word "rein (back)" is usually used to describe someone or something that needs to be controlled or restrained. However, there are numerous synonyms that can be used in place of this phrase. They include words such as check, curb, constrain, control, subdue, manage, govern, regulate, supervise, and direct, among others. These synonyms are useful for writers, speakers, and communicators who want to use more nuanced and varied language. Whether you're describing a wayward horse that needs to be reined in or a difficult employee who needs to be managed, these synonyms can help you find the right word to express your meaning.