Knotty

Adjective

1. Of string or something stringlike: full of, or tied up, in knots.
2. Of a part of the body, a tree, etc.: full of knots (knobs or swellings); gnarled, knobbly.

   "a knotty pine"

3. Complicated or tricky; complex, difficult.

   "a knotty problem"

4. Complicated or tricky; complex, difficult.

   "a knotty problem"

5. Of an austere or hard nature; rugged.