He was not able to cut through the gnarl of the tree.
He was a mean man who tended to gnarl out his answers.
He had a big bump on his knee that looked like the gnarl of an old tree.
The top of the oak table showed the unusual grain that was caused by the gnarl in the oak tree's trunk.
The gnarl in the branch made it harder for the squirrels to run up the branch.