1) Become knotty 2) Bump on a tree 3) Contort 4) Contort into a knot 5) Contort; distort 6) Distort 7) Distorted shape 8) Distortion 9) Exclusively Saxon word 10) Exclusively Anglo word 11) Get all twisty 12) Knot 13) Knot in a tree 14) Knot in a tree trunk 15) Knot on a tree 16) Knot on a trunk 17) Knotty protuberance 1) Complexity 2) Knot 
• (n.) a knot in wood; a large or hard knot, or a protuberance with twisted grain, on a tree. • (v. i.) To growl; to snarl.
Gnarl intransitive verb [ imperfect & past participle Gnarled ; present participle & verbal noun Gnarling .] [ From older gnar , probably of imitative origin; confer German knarren , knurren . Dutch knorren ,...Gnarl noun [ See Gnar , noun ] a knot in wood; a large or hard knot, or a protuberance with twisted grain, on a tree. 
[v] - twist into a state of deformity
verb twist into a state of deformity; `The wind has gnarled this old tree`
a knotty protuberance on a tree; knot.