/ ˌɪnstɪˈtjuːʃn; NAmE -ˈtuːʃn/ noun
1.
[ C ] a large important organization that has a particular purpose, for example, a university or bank :
an educational / financial, etc. institution
the Smithsonian Institution
2.
[ C ] (usually disapproving ) a building where people with special needs are taken care of, for example because they are old or mentally ill :
a mental institution
We want this to be like a home, not an institution.
3.
[ C ] a custom or system that has existed for a long time among a particular group of people :
the institution of marriage
4.
[ U ] the act of starting or introducing sth such as a system or a law :
the institution of new safety procedures
5.
[ C ] ( informal , humorous ) 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!
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WORD ORIGIN
late Middle English (in senses 3 and 4): via Old French from Latin institutio(n-) , from the verb instituere , from in- in, towards + statuere set up. Sense 1 dates from the early 18th cent.