WordWeb Online

1. Making great mental demands; hard to comprehend or solve or believe
   "I faced the knotty problem of what to have for breakfast"
   - baffling, elusive, problematic, problematical, tough
    
2. Used of old persons or old trees; covered with knobs or knots
   - gnarled, gnarly, knotted, knobbed
    
3. Highly complex or intricate and occasionally devious
   "a knotty problem"
   - Byzantine, convoluted, involved, tangled, tortuous
    
4. Tangled in knots or snarls
   - snarled, snarly

Derived forms: knottiest, knottier

See also: complex, crooked, difficult, hard, knot, knottiness, tangled

Encyclopedia: Knotty