immunodiffusionPronunciation: /ˌɪmjʊnəʊdɪˈfjuːʒ(ə)n, ɪˌmjuːnəʊ-/Definition of immunodiffusion noun [mass noun] Biochemistry a technique for detecting or measuring antibodies and antigens by their precipitation when diffused together through a gel or other medium. immunodiffusion in other Oxford dictionaries Definition of immunodiffusion in the US English dictionary