knotty
形容词 knotty:
making great mental demands; hard to comprehend or solve or believe
同义词:baffling, problematic, problematical, tough
used of old persons or old trees; covered with knobs or knots
同义词:gnarled, gnarly, knotted, knobbed
highly complex or intricate
同义词:Byzantine, convoluted, involved, tangled, tortuous
tangled in knots or snarls