Source : Webster's Revised Unabridged Dictionary (1913)

Bivouac \Biv"ouac\, v. i. [imp. & p. p. {Bivouacked} (?); p. pr.
   & vb. n. {Bivouacking}.] (Mil.)
   (a) To watch at night or be on guard, as a whole army.
   (b) To encamp for the night without tents or covering.

Bivouac \Biv"ouac\, n. [F. bivouac, bivac, prab. fr. G.
   beiwache, or beiwacht; bei by, near + wachen to watch, wache
   watch, guard. See {By}, and {Watch}.] (Mil.)
   (a) The watch of a whole army by night, when in danger of
       surprise or attack.
   (b) An encampment for the night without tents or covering.

Source : WordNet®

bivouac
     n 1: temporary living quarters specially built by the army for
          soldiers; "wherever he went in the camp the men were
          grumbling" [syn: {camp}, {encampment}, {cantonment}]
     2: a site where people on holiday can pitch a tent [syn: {campsite},
         {campground}, {camping site}, {camping ground}, {encampment},
         {camping area}]
     v : live in or as if in a tent; "Can we go camping again this
         summer?"; "The circus tented near the town"; "The
         houseguests had to camp in the living room" [syn: {camp},
          {encamp}, {camp out}, {tent}]
     [also: {bivouacking}, {bivouacked}]