남사친 – A guy who is “just a friend”

남 is short for 남자, meaning

“man”

사 is short for 사람, meaning “person”

친 is short for 친구, meaning friend.

Put them all together, and you get man-person-friend, or a male friend.

Guys, you can use the same term for a girl who is your friend but isn’t your girlfriend. Change the 남 to 여 (여자), and you’ve got 여사친!