v.1. To obstruct some passageway: The fallen leaves stopped up the drainpipe. This nagging cold has stopped my sinuses up.
2. To cause something to become obstructed: The reason the engine malfunctioned was that some mud had stopped up its vents. My sloppy roommate stopped the sink up with leftover food.
3. To become obstructed: Call the plumber; the sink stopped up again.
4. To become constipated: I had stopped up, so I took some laxatives.