Fill (or Weft)
Visible yarns in a fabric that are woven through the less visible foundation of the warp yarns. The term “fill” can also apply to how an item is stuffed such as a 100% down-fill pillow.
What’s The Difference Between Warp And Fill? – Acadian Industrial Textiles
Warp And Weft
Filling – Weaving
How To Identify The Warp And Weft Yarn Of a Woven Fabric – Textile Apex
Warp Fill & Bias — Challenge Sailcloth