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verb + 什么 +verb means "stoping doing something" or "why do you still do this"
for example, you have to go to school at 8 o'clock. now it is 7:50 and you just begin to have your breakfast, then you mom could say: why do you still have your breakfast now?/ stop eating, you will be late, GO now! in chinese, we say, 你为什么还在吃早饭？/别吃了 有要迟到了，立刻出发！
but if your mom is a little bit angry, she will say: 吃什么吃！没时间了(no time)，立刻出发！
吃什么吃 means : stop eating or why do you still eat now?
