Antonyms for the word "anti-septic" would be words that signify a lack of cleanliness, disinfection or sterility. These words may include "dirty", "unclean", "infected", "contaminated", "uncleansed", "unsanitary", "tainted" and "polluted". While "anti-septic" means to prevent infection or contamination, its antonyms signal an environment or condition characterized by the presence of germs, bacteria or other harmful substances. It is important to know the antonyms for "anti-septic" to have a clear understanding of the possible detrimental effects of a non-sterile environment and the need for proper sanitation and cleanliness.