How do you spell Bivouac

Available Definitions:
1)  n. - The watch of a whole army by night, when in danger of surprise or attack.
2)  n. - An encampment for the night without tents or covering.
3)  v. i. - To watch at night or be on guard, as a whole army.
4)  v. i. - To encamp for the night without tents or covering.