intumescent UK /ɪntjʊˈmɛsənt/US /ɪntuˈmɛsənt/adjective 1noun 1forms 1 adjective1 •That becomes swollen, especially upon exposure to heat. noun1 •Any substance that swells on exposure to heat, thus increasing in volume and decreasing in density.Intumescents are used in some fire protection systems. formsintumescents
