Noun
1. an organization founded and united for a specific purpose
2. an establishment consisting of a building or complex of buildings where an organization for the promotion of some cause is situated
3. a custom that for a long time has been an important feature of some group or society;
"the institution of marriage""the institution of slavery""he had become an institution in the theater"4. the act of starting something for the first time; introducing something new;
"she looked forward to her initiation as an adult""the foundation of a new scientific society""he regards the fork as a modern introduction"5. a hospital for mentally incompetent or unbalanced person