Synonyms for Complex:

adj.

complex (adjective)
difficult, intricate, puzzling, perplexing, complicated, abstruse, convoluted, involved, mysterious, obscure.
complicated (adjective)
confused, intricate, inextricable, snarled, tangled, confounded, labyrinthine, convoluted, elaborate, involved, knotted, complicated, perplexing.
convoluted (adjective)
tangled.
difficult (adjective)
hard, laborious, toilsome, contrary, tight, fussy, trying, stressful, tricky, bothersome, demanding, strenuous, finicky, grinding, thorny, wearing, severe, wearying, troublesome, knotty, meandering, uphill, rough, formidable, difficult, paradoxical, cumbersome, onerous, oppressive, burdensome, rugged, cantankerous, tough, wearisome, arduous, harsh, complicated, ticklish, adverse.
difficult to understand (adjective)
byzantine, interwoven, puzzling, crabbed, undecipherable, impenetrable, involved, excursive, muddled, obscure, hidden, paradoxical, enigmatic, perplexing, rambling, sinuous, unfathomable, mazy, cryptic, recondite, inscrutable, meandering, disordered, snarled, abstruse, gordian, intricate, winding, knotted.
involved, intricate (adjective)
motley, tortuous, circuitous, mosaic, compound, labyrinthine, composite, elaborate, knotty, convoluted, tangled, miscellaneous, manifold, multiform, multiple, complicated, variegated, confused, multifarious, multiplex.
various (adjective)
multifaceted, polymorphous, assorted, diversified, many-sided, variegated, multiphase, various, polymorphic, manifold, multiform, sundry, motley, Diversiform, diverse, Heteromorphous, multiplex, Multifold, multifarious.

n.

bombardment, avalanche, blizzard, bonanza, cornucopia, cascade, feast, deluge, concentration. defense, damage, catharsis, conditioning, involute, fixated, fixation, delusion, Daedal, exorcism, defense mechanism. declarative, inflected, Frequentative, feminine, grammatical, deictic, conditional. cognition (noun)
composite.
complex (noun)
coordination compound, interwoven, colonial, compound, interlinking, interlocking, composite, analyzable, intricate, multiplex, knotty, gordian, byzantine, mazy, tangled, tortuous, involved, complicated, thickening, convoluted, multifactorial, interlacing, labyrinthine, building complex, decomposable, labyrinthian.
obsession (noun)
fixation.
psychological problem (noun)
fixation.

Other synonyms:

Byzantine
byzantine.
inscrutable, barracks, bonanza, incomprehensible, conditioning, feminine, catharsis, deictic, enigmatic, declarative, Frequentative, impenetrable, grammatical, unfathomable, Daedal, cascade, apartment complex, cornucopia, involute, Daedalian. contorted, exorcism, megaplex, fixation, huddle, bombardment, fixated, blizzard, conditional, avalanche, inflected, defense mechanism. deluge, center, feast, delusion. concentration. development. block, damage. defense. puzzling
confusing.
Other relevant words:
defense, confusing, labyrinthian, mazy, conditioning, tortuous, fixated, block, mosaic, concentration, barracks, confounded, crabbed, interlinking, gordian, meandering, megaplex, excursive, disordered, paradoxical, interlacing, fixation, roundabout, thickening, combined, Frequentative, circuitous, bonanza, involute, feast, hidden, inflected, rambling, building complex, coordination compound, composite, interwoven, sinuous, inscrutable, undecipherable, irreducible, winding, declarative, analyzable, recondite, multiple, Daedal, compound, incomprehensible, decomposable, grammatical, twisted, Daedalian, inextricable, devious, impenetrable, multifactorial, cryptic, colonial, cornucopia, unfathomable, development, enigmatic, byzantine, deictic, delusion, muddled, interlocking, bombardment, miscellaneous.

Usage examples for complex

  1. The causes of the failure of The Liberal were very complex but quite obvious. – Leigh Hunt's Relations with Byron, Shelley and Keats by Barnette Miller
  2. I am afraid it is becoming a complex – The Clock Strikes Thirteen by Mildred A. Wirt
  3. It was not a complex method, and it worked. – The Pirates of Ersatz by Murray Leinster