at the crack of dawn idiom
C2 大清早，黎明，破晓时分
very early in the morning, especially at the time when the sun first appears
We'll have to leave at the crack of dawn. 我们天一亮就得动身。
江苏热线英汉汉英双解词典包含207361条英汉翻译词条，涵盖了常用英语单词及词组短语的翻译及用法，是英语学习的必备工具。