knotty (adj.)

• abstruse
• arduous
• brutal
• burled
• complex
• complicated
• crabbed
• critical
• daedal
• delicate
• demanding
• difficult
• effortful
• elaborate
• exacting
• formidable
• garbled
• gnarled
• gnarly
• gordian
• hairy
• hard
• hard-fought
• intricate
• involved
• jumbled
• knobbed
• knobbly
• knobby
• knotted
• laborious
• labyrinthine
• lumpy
• mean
• nodal
• nodular
• nodulated
• noduled
• nubbly
• nubby
• obscure
• operose
• perplexed
• rigorous
• rough
• rugged
• scrambled
• severe
• sophisticated
• spiny
• steep
• sticky
• strenuous
• studded
• terrible
• thorny
• ticklish
• toilsome
• tough
• tricky
• tubercular
• tuberculous
• tuberous
• uphill
• wicked