Stop up Definition 1 of 3Pro Tip 1/3Physical Repair Used when fixing something by filling or covering holes and gaps. I stopped up the cracks in the wall before painting. Pro Tip 2/3Temporary Solution Often implies a makeshift or temporary fix, not a permanent one. To get through the night, we stopped up the broken window with cardboard. Pro Tip 3/3Prevent Damage Highlights stopping something from getting worse. He stopped up the leaking pipe to prevent water damage.