The antonym for "un-clogged" is "clogged." Clogged refers to something that is completely blocked or obstructed, which hinders its normal functioning. It often implies a buildup or accumulation of something, such as dirt, debris, or other substances. Clogged drains, pipes, and air filters are common examples of clogged objects that can cause problems if left untended. To restore regular activity and functionality, the object in question must be unclogged or cleared out. Therefore, "clogged" and "unclogged" are two opposite ends of the same spectrum, one representing a blockage or hindrance, the other indicating the removal of that blockage to resume normal operation.