The opposite of germ-free is contaminated. The word contaminated refers to the introduction or presence of harmful substances or materials, such as bacteria, viruses, or toxins. The environment or surface that is contaminated is not fit for use or consumption, as it is capable of causing health hazards. Another antonym for germ-free is dirty, which indicates the presence of dirt, grime, or filth, which can harbor harmful bacteria and germs. Unclean is another antonym for germ-free, representing the presence of dust, pollutants or harmful microorganisms that can contaminate a person or object and cause sickness. Thus, the antonyms for germ-free indicate the opposite of cleanliness, hygiene, and sterility.