knotty

gnarled

Twisted and knotty

• burlsKnotty trunk outgrowths
• grainCereal plant's harvest unit
• twistedWound around itself

weathered · oak · pine · timber · hardwood · lumber · plank · carpentry · woodworking · sawmill

snarled

Growled or knotted

• twistedWound around itself
• kinkedBent with tight curves
• mattedTangled into clumps

gnarled · entwined · raveled · coiled · interlaced · enmeshed · snaggy · balled · wadded · jumbled

complicated

Difficult to understand

• intricateElaborately detailed, many parts
• convolutedExcessively complex or twisted
• tangledTwisted confusedly together

thorny · labyrinthine · byzantine · perplexing · confounding · tortuous · entangled · elaborate · multifaceted · nuanced

challenging

Hard to accomplish

• troublesomeCausing difficulty or annoyance
• problematicCausing difficulty or concern
• thornyHaving sharp protrusions

vexing · tricky · sticky · demanding · tough · taxing · formidable · hard · awkward · dicey

enigma

Something hard to fathom

• conundrumPerplexing problem or question
• riddlePuzzling question to solve
• brainteaserPuzzle demanding clever thought

dilemma · paradox · quandary · mystery · gordian · impasse · sticking point · stumper · head-scratcher · poser

• hairhair, haircut, hairstyle, hair loss, coily
• complexitycomplex, complicated, simple, intricate, easy
• tree traitsbranching, rooted, tall, leafy, woody
• wood statesdried, dry, wet, green, raw
• texturessmoothness, smooth, soft, rough, roughness
• challengeschallenge, difficult, hard, challenging, tough