Prophylactic might sound like a prehistoric period when dinosaurs roamed the earth, but it actually describes something that can prevent something negative, such as disease. Prophylactic surgery to remove a mole can prevent skin cancer.
If you want to avoid getting sick, you can get a vaccine, take medicine, or have surgery — all of which are considered prophylactic measures. Delve deeper into the history of this four-syllable word and you'll find the Greek term prophulaktikos, which means to "guard before." Prophylactic can also describe a contraceptive used to prevent pregnancy. This use of the word started because condoms, which are prophylactics, were originally designed to prevent disease, not pregnancy.