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Synonyms for Knotty (same or very similar meaning)

WordNet sense 1 (used of old persons or old trees; covered with knobs or knots):
gnarled, gnarly, knobbed, knotted

WordNet sense 2 (having or marked by bends or angles; not straight or aligned):
crooked, crooked

WordNet sense 3 (highly complex or intricate):
byzantine, convoluted, involved, tortuous

WordNet sense 4 (complicated in structure; consisting of interconnected parts):
complex, complex

WordNet sense 5 (making great mental demands; hard to comprehend or solve or believe):
baffling, problematic, problematical, tough

WordNet sense 6 (not easy; requiring great physical or mental effort to accomplish or comprehend or endure):
difficult, hard

WordNet sense 7 (tangled in knots or snarls):
snarly, snarled

WordNet sense 8 (in a confused mass):

From the ODE community, based on WordNetadd/edit