n. 1. That which is used to fill a cavity or any empty space, or to supply a deficiency; as, filling for a cavity in a tooth, a depression in a roadbed, the space between exterior and interior walls of masonry, the pores of open-grained wood, the space between the outer and inner planks of a vessel, etc. [ 1913 Webster ]
2. The woof in woven fabrics. [ 1913 Webster ]
3. (Brewing) Prepared wort added to ale to cleanse it. [ 1913 Webster ]
Back filling. (Arch.) See under Back, a. [ 1913 Webster ]