a party of former associates who have come together again
"The old classmates gathered at the park for their annual reunion, sharing stories from years past."
the act of coming together again
"monetary unification precipitated the reunification of the German state in October 1990"
The process or act of reuniting.
"The emotional reunion between the long-lost siblings was marked by tears and joyful embraces after decades apart."
In plain English: A reunion is when people who have been apart for a while get together again to see each other.
"The family gathered for a warm reunion after years apart."
The word reunion entered English from the Middle French term réunion, which was formed by combining the prefix meaning "again" with a root for joining together. Although its components are obvious today, it arrived as a distinct borrowing rather than being constructed directly in English at that time.