a tent thing made up of a sheet of plastic some ropes and some pegs, they are used by the army as light weight accomodation I called my brother who is an Army Drill Sergeant trainer. He told me that the word is Bivouac. It is not an acronym. It is argued as to whether this word comes from French or German but it is "an encampment, usually without tents. While in training, in the army myself, I had to go on Bivouac. We camped out (luckily in tents) and preformed training exercises for a week.