antimalarial UK /ˌæn.ti.məˈlɛə.ɹi.əl/US /ˌæn.ti.məˈlɛ.ɹi.əl/adjective 1noun 1forms 3 adjective1 •Preventing or counteracting malaria. noun1 •An agent that prevents or counteracts malaria. formsantimalarials · more antimalarial · most antimalarial