stop up (third-person singular simple present stops up, present participle stopping up, simple past and past participle stopped up)

1. To fill a hole or cavity, or block (an opening or passage), as with a plug.

   Coordinate terms: plug up, stop off

   • 1885, Mark Twain, chapter 37, in Huckleberry Finn:

     So then we […] scratched around and found an old tin washpan, and stopped up the holes as well as we could.

2. (UK, legal) To permanently close or block (a road or path); to legally extinguish a right of way.

   Coordinate terms: block off, close off

3. (photography) To increase the aperture of a photographic lens, moving from an f/stop represented by a higher number to an f/stop represented by a lower number and causing more light to pass into the camera.

• (antonym(s) of “increase the aperture of a photographic lens”): stop down