firewall UK /ˈfaɪə.wɔəl/US /ˈfaɪ(ə)ɹˌwɔl/noun 5verb 3forms 3 noun5 •A fireproof barrier used to prevent the spread of fire between or through buildings, structures, electrical substation transformers, or within an aircraft or vehicle. •The software that monitors traffic in and out of a private network or a personal computer and allows or blocks such traffic depending on its perceived threat. •An unwritten agreement among major political parties to refuse to govern or cooperate with national conservative and ultranationalist parties."Honest government must be preceded by honest negotiations," Mr Kickl said when Austria's president tasked him with beginning coalition talks after the centrist firewall failed. — 2025 •An ethical wall; an organizational or legal separation between two entities that might otherwise cause conflicts of interest. •A hypothetical phenomenon where an observer falling into a black hole encounters high-energy quanta at or near the event horizon. verb3 •To protect with a firewall. •To block with a firewall. •(slang) To use maximum engine power or acceleration. formsfirewalled · firewalling · firewalls