The Collaborative International Dictionary of English v.0.48:

Labyrinthine \Lab`y*rin"thine\, a.
   Pertaining to, or like, a labyrinth; labyrinthal;
   labyrinthian.
   [1913 Webster]

WordNet (r) 3.0 (2006):

labyrinthine
    adj 1: relating to or affecting or originating in the inner ear;
           "labyrinthine deafness"
    2: resembling a labyrinth in form or complexity; "a labyrinthine
       network of tortuous footpaths" [syn: labyrinthine,
       labyrinthian, mazy]

Moby Thesaurus II by Grady Ward, 1.0:

184 Moby Thesaurus words for "labyrinthine":
   Byzantine, Gongoresque, Johnsonian, aberrant, aberrative, affected,
   ambagious, anamorphous, anfractuous, askew, asymmetric, balled up,
   bedizened, bent, big-sounding, billowing, billowy, bowed,
   circuitous, circumlocutory, cockeyed, complex, complicated,
   confounded, confused, contorted, convoluted, convolutional,
   crabbed, crazy, crooked, crumpled, crunched, curvaceous, curvate,
   curvated, curve, curved, curvesome, curviform, curvilineal,
   curvilinear, curving, curvy, daedal, declamatory, departing,
   desultory, deviant, deviating, deviative, deviatory, devious,
   digressive, discursive, distorted, elaborate, elevated, embrangled,
   entangled, errant, erratic, euphuistic, excursive, flamboyant,
   flaming, flashy, flaunting, flexuose, flexuous, fouled up, fulsome,
   garish, gaudy, geosynclinal, gordian, grandiloquent, grandiose,
   grandisonant, high-flowing, high-flown, high-flying, high-sounding,
   highfalutin, implicated, incurvate, incurvated, incurved,
   incurving, indirect, inkhorn, intricate, involute, involuted,
   involutional, involved, irregular, knotted, knotty, labyrinthian,
   lexiphanic, lofty, lopsided, loused up, lurid, magniloquent,
   many-faceted, matted, mazy, meandering, meandrous, meretricious,
   messed up, mixed up, mucked up, multifarious, nonsymmetric,
   one-sided, orotund, ostentatious, out-of-the-way, overdone,
   overelaborate, overinvolved, overwrought, pedantic, perplexed,
   planetary, pompous, pretentious, rambling, ramified, recurvate,
   recurvated, recurved, recurving, rhetorical, rivose, rivulose,
   roundabout, roving, ruffled, screwed up, sensational,
   sensationalistic, sententious, serpentine, shifting, showy,
   sinuate, sinuose, sinuous, snaky, snarled, sonorous, sophisticated,
   sprung, stilted, stray, subtle, swerving, tall, tangled, tangly,
   torsional, tortile, tortuous, turning, twisted, twisting, twisty,
   undirected, undulant, unsymmetric, vagrant, veering, wandering,
   warped, wavy, whorled, winding, wreathlike, wreathy, zigzag