사오정
Someone who is unaware, thickheaded or dull

사이비
Sham, fake, fraud

살벌하다/ 쌀벌하다
(adj) An overwhelming, brutal, tense + violent atmosphere

삽질하다
To bullshit
E.g.  저 새끼 또 삽질하네.  He's bullshitting again.

삼천포로 빠지다
To get off the subject

새끼
a) A derog term for a man.
b) This term is also used in a very close circle of friends, just like the Afro American term 'bro'.

새대가리
A birdbrain

새되다
= 좆되다
Originated from the song '새' by 'Psy.' 
Download the song(MP3).

생판/ 쌩판
Completely
E.g. 쌩판 모르는 씹쌔들이 지랄이네

순진빵
a naive person

술고래
A drunkard

식후땡
A cigarette shortly after a meal
Submitted by Azz

싸가지없다
(adj) someone who is very bitchy and ill-mannered.
Some people like to use '싹바가지없다' or '싹퉁머리없다' in place of '싸가지없다' to make the expression stronger.

싸대기
A slap in the face

싸이코
A psycho