This is the 10904th most frequent Russian word.
выпускной
"Выпускной" means "graduation" or "related to graduation."
Here, 'выпускной' serves as an adjective describing the evening, i.e., the event for graduates.
Выпускной вечер пройдет завтра в школе.
The graduation party will take place tomorrow at the school.
In this sentence, 'выпускной' functions as an adjective related to the exam held for completion or graduation.
У нас в университете выпускной экзамен в конце года.
We have the graduation exam at the end of the year at the university.
Here, 'выпускной' is a noun and refers to the graduation ceremony or event itself.