The Collaborative International Dictionary of English v.0.48:

Byzantine \By*zan"tine\ (b[i^]*z[a^]n"t[i^]n), a.
   Of or pertaining to Byzantium. -- n. A native or inhabitant
   of Byzantium, now Constantinople; sometimes, applied to an
   inhabitant of the modern city of Constantinople. [Written
   also Bizantine.]
   [1913 Webster]

   Byzantine church, the Eastern or Greek church, as
      distinguished from the Western or Roman or Latin church.
      See under Greek.

   Byzantine empire, the Eastern Roman or Greek empire from a.
      d. 364 or a. d. 395 to the capture of Constantinople by
      the Turks, a. d. 1453.

   Byzantine historians, historians and writers (Zonaras,
      Procopius, etc.) who lived in the Byzantine empire. --P.
      Cyc.

   Byzantine style (Arch.), a style of architecture developed
      in the Byzantine empire.

   Note: Its leading forms are the round arch, the dome, the
         pillar, the circle, and the cross. The capitals of the
         pillars are of endless variety, and full of invention.
         The mosque of St. Sophia, Constantinople, and the
         church of St. Mark, Venice, are prominent examples of
         Byzantine architecture.
         [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Byzant \Byz"ant\, Byzantine \Byz"an*tine\ (-[a^]n"t[imac]n)
   n.[OE. besant, besaunt, F. besant, fr. LL. Byzantius,
   Byzantinus, fr. Byzantium.] (Numis.)
   A gold coin, so called from being coined at Byzantium. See
   Bezant.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Byzantine
    adj 1: of or relating to the Eastern Orthodox Church or the
           rites performed in it; "Byzantine monks"; "Byzantine
           rites"
    2: of or relating to or characteristic of the Byzantine Empire
       or the ancient city of Byzantium
    3: highly complex or intricate and occasionally devious; "the
       Byzantine tax structure"; "Byzantine methods for holding on
       to his chairmanship"; "convoluted legal language";
       "convoluted reasoning"; "the plot was too involved"; "a
       knotty problem"; "got his way by labyrinthine maneuvering";
       "Oh, what a tangled web we weave"- Sir Walter Scott;
       "tortuous legal procedures"; "tortuous negotiations lasting
       for months" [syn: Byzantine, convoluted, involved,
       knotty, tangled, tortuous]
    n 1: a native or inhabitant of Byzantium or of the Byzantine
         Empire

Moby Thesaurus II by Grady Ward, 1.0:

68 Moby Thesaurus words for "Byzantine":
   Machiavellian, artful, balled up, calculating, canny, collusive,
   complex, complicated, confounded, confused, connivent, conniving,
   conspiring, contriving, convoluted, crabbed, crafty, cunning,
   daedal, designing, devious, elaborate, embrangled, entangled,
   fouled up, foxy, gordian, guileful, implicated, insidious,
   intricate, intriguing, involuted, involved, knotted, knotty,
   knowing, labyrinthian, labyrinthine, loused up, many-faceted,
   matted, mazy, meandering, messed up, mixed up, mucked up,
   multifarious, pawky, perplexed, plotting, ramified, roundabout,
   scheming, screwed up, shrewd, slick, sly, snarled, sophisticated,
   stratagemical, subtile, subtle, tangled, tangly, twisted, up to,
   wily



The Free On-line Dictionary of Computing (30 December 2018):

Byzantine

    A term describing any system that has
   so many labyrinthine internal interconnections that it would
   be impossible to simplify by separation into loosely coupled
   or linked components.

   The city of Byzantium, later renamed Constantinople and then
   Istanbul, and the Byzantine Empire were vitiated by a
   bureaucratic overelaboration bordering on lunacy: quadruple
   banked agencies, dozens or even scores of superfluous levels
   and officials with high flown titles unrelated to their actual
   function, if any.

   Access to the Emperor and his council was controlled by
   powerful and inscrutable eunuchs and by rival sports factions.

   [Edward Gibbon, "Decline and Fall of the Roman Empire"].

   (1999-01-15)