Of a part of the body, a tree, etc.: full of knots (knobs or swellings); gnarled, knobbly.
Of string or something stringlike: full of, or tied up, in knots.
Complicated or tricky; complex, difficult.
Of an austere or hard nature; rugged.
gnarled, knotted; wizened, wrinkled.
Of an object: derisorily small, tiny; of a person: puny, stunted.