IPA: /ˌɪm.juː.nəˈkɒm.pɪ.tənt/
KK: /ɪˌmjunəˈkɑmpɪtənt/
Having the ability to respond effectively to infections and diseases due to a properly functioning immune system.
People who are immunocompetent can usually fight off infections more easily than those who are not.
Immunocompetent is formed from "immunis" (from Latin, meaning exempt or free from) and "competent" (from Latin "competens", meaning suitable or capable). The term describes an organism that is capable of mounting an immune response, thus being suitable to defend against pathogens.
Think of 'immunis' meaning free from disease and 'competent' meaning capable — together, they describe someone who is capable of defending against illness.