Hi... I'm new. (^_^) I'm a college student on the West Coast of the US. I'm only in my third year of Japanese, but I'm really interested in the language and culture. Since my classes focus mostly on polite speech, I would like to learn some really casual Japanese slang words. So far I only know ちょう、まじで、and すげい・・・Can anyone add to my repertoire? Thanks!
A big part of casual speech has to do, not with the words but with how you say them. Street Japanese often changes the verb suffix to an え sound, ie わからない changes to わからね. Another common casual form is to add んです to the end of every sentence. わからねんですか?
That said, here's a small list of pretty common words:
酷い(ひどい)
It's used in a similar way to 'lame' or 'that sucks'. Another, very similar, is 微妙(びみょう), which is sort of teenage girl slang (which I found out the hard way after a language exchange partner taught it to me and I went around using it, to the great amusement of my Japanese coworkers.)
糞(くそ)
It can be used as an adjective, ie クソ寒い, roughly equivalent to 'it's fucking cold' (though the literal translation is more like 'it's shitting cold'.)
嘘(うそ)
This means 'lie' and gets a lot of use, primarily in the sense of 'get out of here' or 'no way'. It's mostly used by women.
And if you want to tell someone off, a couple of good ones are 馬鹿(ばか), which can be used in the sense of 'you idiot', 'dumbass' or 'crazy', and 馬鹿野郎(ばかやろう)which is much stronger, more like 'motherfucker.' てめい is sort of similar, the translation is 'you bastard' and the 'you' part of that is really important to keep in mind (as I found out the hard way.)