Impossible to contact or find.
My phone was out of battery, making me unreachable for a while.
휴대폰 배터리가 다 떨어져서 잠시 연락이 되지 않았습니다.
Not possible to get to, often because of distance or obstacles.
The top of the mountain was unreachable due to the steep cliffs.
험준한 절벽 때문에 산의 정상에 도달할 수 없었습니다.
Beyond someone's understanding or ability to grasp.
The idea of infinity is unreachable for many people.
무한이라는 개념은 많은 사람들에게는 이해하기 어렵습니다.