To make a last-minute effort when it's already too late; to take action only when a problem is critical and imminent, which proves futile.
平时不注重学习，等到考试临近才熬夜抱佛脚，这不就是临噎掘井吗？
Not focusing on studying normally, then pulling all-nighters right before the exam, isn't that just digging a well when you're about to choke?
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