공주병(암)
The depreciatory name for a pompous conceited woman.
공주암 (암 = cancer) is used for added contempt.
The male equivalent is 왕자병(암).

구라
A lie

구라 + 까다/ 치다
To lie to someone
E.g. 구라치지마.

구름과자
A cigarette
This is not 'at all' a popular term and was submitted by 혜산.

구리다
poor quality, uncool, boring, ugly, messed up, not right, bad
E.g  존나 구려.  It really sucks.

굼벵이
a snail or an idle person

기스
A dent, a crevice, a crack

김새다
To lose vitality and become dull or tepid as a result of the discovery of a surprise or a secret

(말) 까다
a. 반말하다.
E.g. 갑이네. 말 까도 되지?
syn. (말) 놓다
b. to kick (with a foot)

까먹다
To forget
E.g.  A. Why didn't you do your home work?  B. I forgot.
A. 왜 숙제 안했어?  B. 까먹었어.

까치
a. a cigarette
b. a counting unit for cigarettes
E.g. 담배 한까치만.  Spare me a cigarette will ya?