Byzantine

of or relating to Byzantium.
of or relating to the Byzantine Empire.
noting or pertaining to the architecture of the Byzantine Empire and to architecture influenced by or imitating it: characterized by masonry construction, round arches, impost blocks, low domes on pendentives, the presence of fine, spiky foliage patterns in low relief on stone capitals and moldings, and the use of frescoes, mosaics, and revetments of fine stone to cover whole interiors.
Fine Arts. pertaining to or designating the style of the fine or decorative arts developed and elaborated in the Byzantine Empire and its provinces: characterized chiefly by an ecclesiastically prescribed iconography, highly formal structure, severe confinement of pictorial space to a shallow depth, and the use of rich, often sumptuous color.
(sometimes lowercase) complex or intricate:
a deal requiring Byzantine financing.
(sometimes lowercase) characterized by elaborate scheming and intrigue, especially for the gaining of political power or favor:
Byzantine methods for holding on to his chairmanship.
of or relating to the Byzantine Church.
a native or inhabitant of Byzantium.
Contemporary Examples

America’s Economy Is Outperforming Rivals Because the U.S. Is Excelling at Globalization Robert Shapiro June 7, 2013
When the Romans Were Turks Blake Gopnik August 29, 2012
Barbara Tuchman’s ‘The Guns of August’ Is Still WWI’s Peerless Chronicle James A. Warren September 28, 2014
The Pentagon’s New Disservice to Soldiers Leslie H. Gelb July 23, 2010
Putin’s Crimea Is a Big Anti-Gay Casino Anna Nemtsova September 7, 2014

Historical Examples

Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 4 Various
Byzantine Churches in Constantinople Alexander Van Millingen
The Inferno August Strindberg
Shakespeare Jest-Books; Unknown
History Of Egypt, Chalda, Syria, Babylonia, And Assyria In The Light Of Recent Discovery L.W. King and H.R. Hall

adjective
of, characteristic of, or relating to Byzantium or the Byzantine Empire
of, relating to, or characterizing the Orthodox Church or its rites and liturgy
of or relating to the highly coloured stylized form of religious art developed in the Byzantine Empire
of or relating to the style of architecture developed in the Byzantine Empire, characterized by massive domes with square bases, rounded arches, spires and minarets, and the extensive use of mosaics
denoting the Medieval Greek spoken in the Byzantine Empire
(of attitudes, etc) inflexible or complicated
noun
an inhabitant of Byzantium
adj.