fire ‧ wall /ˈfaɪəwɔːl $ ˈfaɪrwɒːl/ BrE AmE noun [countable]
1 . a special wall that prevents fires from spreading to other parts of a building
2 . a system that protects a computer ↑ network from being used or looked at by people who do not have permission to do so
3 . a system that is used by large financial or law companies to stop secret information from being passed from one department to another