The term "shotgunned" refers to the act of drinking an entire can or bottle of drink in one go. An antonym for this could be sipping, which refers to drinking in small quantities at a time. Another antonym could be pacing, which involves drinking slowly and steadily. Savoring could also be an antonym, meaning to enjoy the taste of a beverage and not just gulping it down. Additionally, rationing could be an antonym, which refers to dividing a drink into smaller portions to conserve it over a period of time. These antonyms all suggest a more measured and thoughtful approach to drinking rather than quickly consuming a beverage.