How do Koreans say "dumbfounded"?

While reading a story called "당나귀 알," I came across the phrase, "수박 장수는 너무 기가 차서...," and become curious about the word 기차다. I became curious because I could not remember ever seeing the word before, even though I most probably have. It may just be one of those words that I have looked up a dozen times, but never really paid enough attention to. Anyway, I want to remember it this time by giving it a little attention.

기차다 means "dumbfounded," "stunned," or "shocked," and, therefore, seems to have the same meaning as 기막히다, which I have heard many times before. Actually, when I first saw 기차다, the word 숨차다 (be out of breath) came to mind, and I thought the writer may have made a mistake by writing 기차다 instead of 기막히다. Of course, after looking up the word, I realized that I was the one who made the mistake.

By the way, I noticed that another definition for 기차다 is 정떨어지다, which means "become disgusted ," "fall out of love ," or "grow sick of." I mention this because 정떨어지다 is a good word that is used a lot in Korea.

From now on, I think I will finally be able to remember 기차다.