1.
under repair; being repaired; closed for repairs
Indicates that something is currently in the process of being repaired or maintained. Commonly seen on signs and notices.
A compound of 修理 (repair) and 中 (in the middle of, during). The suffix 中 is highly productive and attaches to many nouns to indicate an ongoing state.
Usage
Very commonly seen on signs posted on equipment, facilities, roads, and buildings. Often appears on its own as a sign: 修理中. Can be used as a no-adjective with の: 修理中の車 (a car under repair).