What is "stop up"

vb. 1 To fill a hole or cavity, or block an opening or passage, as with a plug. 2 (context photography English) 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 camer

v. fill or close tightly with or as if with a plug; "plug the hole"; "stop up the leak" [syn: plug, secure]