I. biv ‧ ou ‧ ac 1 /ˈbɪvu-æk/ BrE AmE noun [countable]
[ Date: 1700-1800 ; Language: French ; Origin: Low German biwake , from bi 'at' + wake 'guard' ]
a temporary camp built outside without any tents
II. bivouac 2 BrE AmE verb ( past tense and past participle bivouacked , present participle bivouacking ) [intransitive]
to spend the night outside without tents in a temporary camp:
The climbers bivouacked halfway up the mountain.