a board used to close off a fireplace when it is not in use
3. civil engineering
a type of board used to encase e.g. structural steelwork as insulation against heat or fire
fireboard in American English
(ˈfaiᵊrˌbɔrd, -ˌbourd)
noun
1.
a board used to close a fireplace
2. chiefly Midland U.S.
a mantel; mantelpiece
Word origin
[1820–30; fire + board]This word is first recorded in the period 1820–30. Other words that entered Englishat around the same time include: analogue, insider, karma, morphology, phonetic