1 [count] a : an established organization
▪ an educational/academic institution ▪ banks and other financial institutions ▪ an institution of higher learning
b : a place where an organization takes care of people for a usually long period of time
▪ She committed herself to a mental institution. [=a hospital for people with mental or emotional problems] ▪ a correctional institution [=a prison] 2 [count] a : a custom, practice, or law that is accepted and used by many people
▪ Family visits are a Thanksgiving institution. ▪ She's not interested in the institution of marriage. ▪ the institution of slavery
b : someone or something that is very well known and established in a particular field or place
▪ He is an institution in local politics. [=he has participated in local politics for such a long time that people consider him to be a regular part of local politics] ▪ The play has become something of an institution on Broadway. 3 [noncount] : the act of beginning or creating something (such as a new law, rule, or system) : the act of instituting something
▪ the institution of new rules and regulations