Definitions of filling:

• noun:   the act of filling something
• noun:   (dentistry) a dental appliance consisting of any of various substances (as metal or plastic) inserted into a prepared cavity in a tooth

  Example: "When he yawned I could see the gold fillings in his teeth"

• noun:   a food mixture used to fill pastry or sandwiches etc.
• noun:   flow into something (as a container)
• noun:   any material that fills a space or container
• noun:   the yarn woven across the warp yarn in weaving