The word "ahjussi" is uncle in Korean but can refer to any man who is like an uncle and basically means you are getting old if someone calls you "adjushi". If not then they will call you "student". The word "kkon-dae" is much harsher and is used by teenagers talking about their teachers behind their backs.

Thanks for teaching me the slang word "ikpa". It sounds like the Korean word "nome" meaning guy but it can be a slight curse adding "bad guy".... "nappum nome". !LUV