Slang/Words you shouldn't use

*** I only get taught by a few people and this can get quite generalized, so if anything is wrong, please, do correct me ***
*** If you want to add anything, that's ok too ;) ***

They didn't want to teach me the really bad words, so the list is quite short.

I'll put the first ones in order of offensiveness.

나쁜 놈. Bad guy. Guy is actually 남자, but this is a worse version of 'man'. This is not that offensive.
미친 놈. Crazy guy.
I think these 2 are used a lot amongst guys when they do something crazy, but it's not insulting or anything. Can't really come up with an example though.
If you say 나쁜 년 to a girl though, she will probably feel insulted.

개새끼. If someone did you wrong or anything and you want to address him, it would be '개새꺄'.
They put '개' (which means dog) in front of a couple of words to make them offensive. It's not that they do not like dogs, it's just a Korean thing. Literally it means 'baby dog' or 'puppy'. The non-offensive word for puppy would be '강아지'.

Last I know of would be 씨발 ofcourse, being like a really offense word. Like sun of a bitch, but they get really offended by it.

Then they have like al lot of versions for 'very'.
아주, 진짜, being the once they teach you at school. They said 진짜 was slang too, but I hear it soooo much, so I dunno.
Then there is 대따, 짱, 되게 which are used quite a lot, especially 대따.
Getting a bit worse there is 개 (Yes they even use it for 'very', but now we already crossed the line of 'words you shouldn't use in class').
The worse versions for 'very' would be 죠낸 and 졸라.

대박 = wow
꺼져 = get out of here
닥쳐 = shut up!
짜증나 = annoying

무슨 말이야 = What are you talking about?
= 뭐라까노 in kyungsang dialect.
그냥 둘러부는거예요 = I'm just looking. You can use this when they annoy you again at the shops...
주문햘게요 = Can I order? *This can be used at a restaurant and isn't bad or anything*

밥 먹자 means 'dig in'/'lets eat', but if you say '법 먹자 it's not okay, because it sounds like you would be eating like a pig, in a voracious way.

That's it for now. I hope to add more later ;)

*** 7/7/10 ***

It's actually quite funny that every time when you say that you know about some korean 'dirty' word, they all get surprised and ask where you learned it, but you can hear Koreans use it quite a lot I think, so why are they so surprised? For example '개새꺄' and '씨발'. These are used quite a lot in movies that you can not have missed it (They tend not to translate '씨발' though or at least wrongly, which is quite funny too be honest). I even heard these in Korea already a couple of times. If you just go out at night, you can hear them. I think I heard it about 2-3 times already. Actually I feel bad about not having native guy friends. They could teach me so much...

You know how that in general you have 2 types of Koreans my age. 1 group that studies really hard and 1 that doesn't.
The term '날라리' is used on more extreme cases of the second. It's used for girls/boys who don't care about studying, go out, have fun, drink, smoke, party, ... Usually used on girls, but apparently also on boys. I first thought she just referred to slutty miniskirted korean girls, like every country has a word for those type of girls (I forgot the Lithuanian one though :( ), but 써니누나 told me that this also could have a 'cute' meaning, but I didn't really understand the cuteness about it. So I was a bit confused about it's real meaning afterwards. I'm quite sure about the fact that it refers to people who neglect their studying, drink and go party though.

*** 8/7/10 ***