The phrase "in jiffy" refers to something that happens quickly or instantly. Its antonyms, on the other hand, describe a sense of slow or gradual action. These antonyms may include delayed, prolonged, gradual, or extended. When something takes a long time to happen, it can be described as gradual or delayed. It may also take an extended period to complete, thus described as prolonged. Alternatively, things may happen leisurely, rather than in a jiffy. To describe a lack of haste, words like leisurely, slowly, or steadily can be utilized instead of in jiffy. In conclusion, the antonyms for in jiffy describe action that is slow and in a way, the opposite of swift.