0 the time in the morning when light begins to appear and the cock (= a male chicken) crows (= makes a sound):
We rise at cockcrow.
What did that cockcrow mean?
Boarding a ship's nothing, but to dig a grave on the land before cockcrow, with the man you're to put in it looking at you!
The epistles shall be ready by night, and you shall ride at cockcrow.
At cockcrow came the call which in that orchard was now as familiar as the rooster's.