an amorphous, cellulose-like, organic substance which acts as a binder for the cellulose fibers in wood and certain plants and adds strength and stiffness to the cell walls
Origin:
lign(i)- + -in
See lignin in American Heritage Dictionary 4
noun
A complex polymer, the chief noncarbohydrate constituent of wood, that binds to cellulose fibers and hardens and strengthens the cell walls of plants.