Synonyms for Formal (same or very similar meaning)
WordNet sense 1 (a lavish dance requiring formal attire):
ball
WordNet sense 2 (a gown for evening wear):
dinner dress, dinner gown, evening gown
WordNet sense 3 (represented in simplified or symbolic form):
schematic
WordNet sense 4 (of or relating to a style of art in which objects do not resemble those known in physical nature):
nonrepresentational
WordNet sense 5 (having official authority or sanction):
official
WordNet sense 6 (capable of or reflecting the capability for correct and valid reasoning):
logical
WordNet sense 7 (rigidly formal):
buckram, stiff
WordNet sense 8 (as a formality only):
perfunctory
WordNet sense 9 (existing in name only):
nominal
WordNet sense 10 (rigidly formal or bound by convention):
ceremonious, conventional
WordNet sense 11 (marked by pomp or ceremony or formality):
ceremonial
WordNet sense 12 (refined or imposing in manner or appearance; befitting a royal court):
courtly, stately
From the ODE community, based on WordNet
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