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
4.the act of starting something for the first time; introducing something new;
she looked forward to her initiation as an adult
5.a hospital for mentally incompetent or unbalanced person