knotty
adjective uk/ˈnɒt.i/ us/ˈnɑː.t̬i/
(COMPLICATED)
informal错综复杂的；难于解决的，棘手的
(of a problem or difficulty) complicated and difficult to solve
It was a very knotty problem. 那实在是一个棘手的问题。
(WOOD)
多节的
with a lot of knots
a knotty piece of wood 多节的木头