Used other than figuratively or idiomatically: see in, contention.
Contending for a title or championship.
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.