noun
serious injury; major injury
Refers to a significant physical injury, often one requiring medical attention or causing lasting damage.
交通事故で大怪我を負った。
I suffered a serious injury in a traffic accident.
幸い、大怪我には至らなかった。
Fortunately, it didn't result in a major injury.
Compound of 大 (おお, 'big, great') and 怪我 (けが, 'injury'). The reading おおけが follows standard rendaku rules.