in·fec·tive \ə̇nˈfektiv\adjective Etymology: Middle English, from Medieval Latin infectivus, from Latin infectus (past participle of inficere to stain, dye, taint, infect) + -ivus -ive — more at infect 1.: producing infection : able to produce infection : infecting 2.: affecting others : infectious • in·fec·tive·nessnoun-es