immunosuppression noun [U] uk / ˌɪm.jə.nəʊ.səˈpreʃ. ə n / us / ˌɪm.jə.noʊ.səˈpreʃ. ə n / specialized › a situation in which the body's immune system is intentionally stopped from working, or is made less effective, usually by drugs, especially in order to help the body accept an organ that has been taken from another person's body: