What does 산전수전 (山戰水戰) literally mean?

ANSWER: mountain (山) battles (戰) sea (水) battles (戰)

The Sino-Korean phrase 산전수전 (山戰水戰) can translate as "fighting all sorts of hardships," but it literally means "mountain (山) battles (戰) [and] sea (水) battles (戰)," which suggests that someone who has fought such battles has experienced great hardship.

Here is a sentence from a Korean book I am reading that uses the expression. The English translation is mine.

어머니께서는 산전수전을 겪으시며 우리를 훌륭히 키우셨다.

Though she was experiencing all sorts of hardships, our mother raised us remarkedly well. 

From Dong-A's Prime Korean-English Dictionary