Pronunciation
man-boong
Definition
멘 stands for abbreviation of english word “mental” , 붕 stands for abbreviation of korean word “붕괴(means collapse or destroyed) ”
so, 멘붕 means that my mind or mental has collapsed. you can use this word when you are very surprised or afraid of bad situation.
you can also say 멘탈붕괴(mental-boongye) as full name of 멘붕
Examples
그놈이 나를 속이다니 멘붕이다.