noun
student at the same middle school; graduate of the same middle school
Colloquial term used among young people to refer to someone who attended or graduated from the same junior high school. Often used in introductions or when discovering a shared background.
あ、田中もおな中なんだ！
Oh, Tanaka is from the same middle school too!
おな中の友達と久しぶりに会った。
I met up with a friend from the same middle school for the first time in a while.
The full, formal phrase meaning 'the same middle school'. おな中 is a casual abbreviation used in conversation.
Abbreviation of 同じ中学校 (onaji chūgakkō, 'the same middle school'), with おな representing 同じ and 中 representing 中学校. The reading おなちゅう is a contraction of おなじちゅう.