남사친

namsachin

What it means

A guy friend — a male friend who's just a friend.

Where it comes from

Short for 남자 사람 친구 (male person friend), to separate it from 남자친구 (boyfriend).

When you'd use it

Clarifying that someone isn't your boyfriend.

Example

걔는 그냥 남사친이야.He's just a guy friend.

Careful

Casual — fine with friends, out of place in formal writing or with your boss.