The phrase "stopped up" is often used to describe a blockage or obstruction in a passageway or opening. Antonyms for the phrase include "unblocked", "cleared", and "opened up". These terms imply that the flow of air, water, or other substance has been restored to its natural state, and that any obstacles preventing this flow have been removed. Other antonyms for "stopped up" may include "free-flowing", "unrestricted", or "unobstructed". These words highlight the idea of movement and fluidity, and suggest a sense of ease or unimpeded motion that contrasts with the sense of restriction conveyed by "stopped up".