a large important organization that has a particular purpose, for example a university or bank

a hospital, prison or other building where people are made to stay and are cared for

They had him committed to an institution.

We want this to be like a home, not an institution.

a custom or system that has existed for a long time among a particular group of people

He claimed this threatened ‘the sacred institution of marriage’.

Fish and chips became a national institution in Britain.

the act of starting or introducing something such as a system or a law

the institution of new safety procedures

a person who is well known because they have been in a particular place or job for a long time

You must know him—he's an institution around here!

LEARNit Dictionary