The term "jam up" is often used colloquially to refer to a situation where progress is impeded or disrupted. Some antonyms for "jam up" might include "smooth sailing," "uninterrupted progress," or simply "success." Other possible antonyms could include "flowing freely," "moving quickly," or "operating smoothly." Ultimately, the antonyms for "jam up" will depend on the context in which the term is being used. Whether the situation is related to traffic, technology, or something else entirely, the opposite of being jammed up is usually a state of ease, efficiency, and progress.