The phrase "jammed up" typically refers to being stuck or hindered in some way. Some possible antonyms for this phrase include "smooth sailing," "flowing freely," "unrestricted," "unhindered," and "unimpeded." These words suggest a sense of freedom or ease, rather than the feeling of being trapped or constricted. Other possible antonyms might include phrases like "moving forward," "unobstructed," or "unencumbered," which similarly convey a sense of progress and momentum. Overall, the antonyms for "jammed up" reflect a desire for mobility, movement, and flexibility that contrasts with the sense of constraint implied by the original phrase.