1. The vagina of any woman called Dawn, or simply Dawn's crack. What you wake up to every morning if you were dating her. The cock usually crows at this time.
2. The vagina of any woman you wake up to in the morning.
3. An expression to describe when a woman's vagina is very close you your face when you wake up and it's the first thing you see.
He's normally late for work cos his cock crows every morning at the crack of Dawn.