The convulsions brought on when one has waited too long to urinate and is incapable of undoing their pants in time.
Matt stood over the toilet, anxious to relieve himself. He zipped partway down, but it stuck. He pulled and tugged but the fly would not undo. He got chills as he fidgeted at the impossible zipper and trembled as his full bladder felt ready to burst. Matt undid the button and tried to pull his pants down far enough to release. When he was finally able to do so, narrowly escaping sullied pants, Matt could feel his urineurysm subside as he relieved himself.
He sighed and trembled as his stream flowed, and almost felt as if he would cry. The seconds ticked away and soon a full minute passed and Matt shuddered at what he believed to be the worst urineurysm he ever had.