The term "retarded flow" refers to a flow that is slow, sluggish, or impeded in some way. Antonyms for this term would include words that describe a flow that is rapid, free-flowing, or unimpeded. Some possible antonyms for "retarded flow" might include terms like "fast flow," "accelerated flow," "unrestricted flow," "swift flow," "streamlined flow," or "unhindered flow." These words suggest a sense of movement, energy, and speed, which stands in contrast to the slow, stagnant nature of a "retarded flow." By using these antonyms in place of "retarded flow," writers can convey a sense of vitality and motion in their descriptions.