When we hear the phrase "reined in", we likely think of a horse being controlled by its rider with the reins. In a broader sense, it can refer to controlling or limiting something or someone. Synonyms for "reined in" include tamed, restrained, curbed, contained, controlled, managed, moderated, checked, and regulated. These words all imply a level of discipline or regulation, whether it's in personal behavior or in a larger system or organization. No matter the context, the idea of "reining in" something or someone suggests an understanding of boundaries and a conscious effort to exercise control and restraint.