Byzantine, subtle, labyrinthine, twisty, gnarly, tortuous, carpentry, mired, snarly, elaborate, Daedalian, voluminous, debatable, confusing, contorted, sawdust, bad, problematic, problematical, involved, baffling, intricate, toughened, crooked, winding, sturdy, confused, daedal, involute, preserve, tangled, simple, knotted, sand, mortice, joinery, elusive, incomprehensible, mortise, dovetail, convolute, snarled, convoluted, knobbed, ruffianly, season, gnarled, twisting
difficult (part of speech: adjective)
formidable, thorny, cumbersome, contrary, strenuous, arduous, laborious, demanding, harsh, rough, uphill, ticklish, tricky, finicky, hard, fussy, troublesome, difficult, wearing, tough, stressful, wearying, complicated, complex, cantankerous, tight, severe, burdensome, wearisome, grinding, adverse, toilsome, onerous, rugged, oppressive, trying, bothersome
- But before they had settled the knotty point, the engine- driver, growing tired of waiting, let off a shrill whistle from his engine and with the sound the little sleeper stirred, opened her eyes, and sat up suddenly. - "The Story of Jessie", Mabel Quiller-Couch.
- Their growth of timber is oak, tall, small, and knotty, and chestnut. - "Memoir, Correspondence, And Miscellanies, From The Papers Of Thomas Jefferson", Thomas Jefferson.
- Historians and antiquaries having alike failed to solve these knotty questions, it is proposed to refer them to a council of Spiritualists, with power to send for persons and papers. - "Nooks and Corners of the New England Coast", Samuel Adams Drake.