"Up spring" means to rise or jump up, so the antonyms for this term would be anything that involves going down, falling or sinking. Some antonyms that come to mind include words like descend, drop, fall, decline, plummet, plunge, sink and lower. These words all suggest a downward motion, which is the opposite of springing up. Other antonyms could include words like lie down, sit down, rest or relax, which imply a state of rest or stillness rather than movement. In summary, the antonyms for "up spring" would be any words that suggest a downward motion or a state of rest rather than leaping upwards.