lignin A complex, cross-linked polymer, comprising phenyl propene units, that is found in many plant-cell walls. Its function appears to be to cement together and anchor cellulose fibres and to stiffen the cell wall. Lignin reduces infection, rot, and decay. It is among the most chemically inert of plant substances and survives in fossils of woody stems.

lignin Complex, non-carbohydrate substance that occurs in woody tissues (especially xylem of plants), often in combination with cellulose. It is lignin that gives wood its strength. To obtain pure cellulose for the paper and rayon industries, the lignin has to be removed from wood.

lignin (Or lignocellulose); indigestible part of the cell wall of plants (a polymer of aromatic alcohols). It is included in measurement of dietary fibre, but not of non‐starch polysaccharide.

lig·nin / ˈlignin/ • n. Bot. a complex organic polymer deposited in the cell walls of many plants, making them rigid and woody.

lignin A complex organic polymer that is deposited within the cellulose of plant cell walls during secondary thickening. Lignification makes the walls woody and therefore rigid. See sclerenchyma.