disinfectant, any substance, such as creosote or alcohol, applied to inanimate objects to kill microorganisms. Disinfectants and antiseptics are alike in that both are germicidal, but antiseptics are applied primarily to living tissue. The ideal disinfectant would rapidly destroy bacteria, fungi, viruses, and protozoans, would not corrode surgical instruments, and would not destroy or discolour materials on which it is used.