immune system immune suppressant drug • immunisation · · · Info · Definitions · Characters · · immune system · · Text Common · · Latin · · Scripts 13 · · Length 4 · · Syllables Definitions · · · (noun) a system (including the thymus and bone marrow and lymphoid tissues) that protects the body from foreign substances and pathogenic organisms by producing the immune response. Synonyms: immune system. · · Noun Definition 1 Characters · · space U+0020 e latin small letter e U+0065 i latin small letter i U+0069 m latin small letter m U+006D n latin small letter n U+006E s latin small letter s U+0073 t latin small letter t U+0074 u latin small letter u U+0075 y latin small letter y U+0079