hmmm i think mal 말 = speak or tell and ya 야 its ending like 이다 or 입니다 and so on = is but sometimes give the meaning "matter" ex 무슨 말야? whats matter? but mwo su in fact i dont know it ^\\^ any way hope that was helpful and if any one see that my answer was wrong please correct it :)) note:: u can write in korean here http://www.wandel.person.dk/korean.html

-mwo su mal-ya mwo sun mal e ya is correct. It means "What do you mean?".

~mal ya (~말야) : You can use it when you want to emphasis something you want to talk to. ex) Mr.Kim mal ya : It means you want to talk about Mr. Kim, so you can use this sentence to start the conversation about him. I think it can be freely translated as "You know, Mr. Kim right?" something like that. And I am not sure about "mwo su mal-ya"?... Do you mean "mu ut eul mal-ya?" (무엇을 말이야?)