fir ‧ ma ‧ ment /ˈfɜːməmənt $ ˈfɜːr-/ BrE AmE noun
[ Date: 1200-1300 ; Language: Late Latin ; Origin: firmamentum , from Latin firmare 'to support' ; ⇨ ↑ firm 1 ]
the firmament literary the sky or heaven
fir ‧ ma ‧ ment /ˈfɜːməmənt $ ˈfɜːr-/ BrE AmE noun
[ Date: 1200-1300 ; Language: Late Latin ; Origin: firmamentum , from Latin firmare 'to support' ; ⇨ ↑ firm 1 ]
the firmament literary the sky or heaven
Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012