The Collaborative International Dictionary of English v.0.48:

Formality \For*mal"i*ty\, n.; pl. Formalities. [Cf. F.
   formalit['e].]
   1. The condition or quality of being formal, strictly
      ceremonious, precise, etc.
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   2. Form without substance.
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            Such [books] as are mere pieces of formality, so
            that if you look on them, you look though them.
                                                  --Fuller.
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   3. Compliance with formal or conventional rules; ceremony;
      conventionality.
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            Nor was his attendance on divine offices a matter of
            formality and custom, but of conscience.
                                                  --Atterbury.
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   4. An established order; conventional rule of procedure;
      usual method; habitual mode.
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            He was installed with all the usual formalities.
                                                  --C.
                                                  Middleton.
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   5. pl. The dress prescribed for any body of men, academical,
      municipal, or sacerdotal. [Obs.]
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            The doctors attending her in their formalities as
            far as Shotover.                      --Fuller.
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   6. That which is formal; the formal part.
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            It unties the inward knot of marriage, . . . while
            it aims to keep fast the outward formality.
                                                  --Milton.
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   7. The quality which makes a thing what it is; essence.
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            The material part of the evil came from our father
            upon us, but the formality of it, the sting and the
            curse, is only by ourselves.          --Jer. Taylor.
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            The formality of the vow lies in the promise made to
            God.                                  --Bp.
                                                  Stillingfleet.
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   8. (Scholastic. Philos.) The manner in which a thing is
      conceived or constituted by an act of human thinking; the
      result of such an act; as, animality and rationality are
      formalities.
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WordNet (r) 3.0 (2006):

formality
    n 1: a requirement of etiquette or custom; "a mere formality"
         [syn: formality, formalities]
    2: a manner that strictly observes all forms and ceremonies;
       "the formality of his voice made the others pay him close
       attention" [syn: formality, formalness] [ant:
       informality]
    3: compliance with formal rules; "courtroom formality"

Moby Thesaurus II by Grady Ward, 1.0:

150 Moby Thesaurus words for "formality":
   Procrustean law, act, baccalaureate service, bienseance, bill,
   bylaw, canon, celebration, ceremonial, ceremony, circumstance,
   civility, code, commencement, conformity, convenance, convention,
   conventional usage, conventionalism, conventionality, convocation,
   correctness, criterion, custom, decency, decorousness, decorum,
   decree, demureness, dictate, dictation, duty, earnestness, edict,
   elegance, empty formality, enactment, etiquette, euphemism,
   euphuism, exactness, exercise, exercises, exquisiteness, form,
   form of worship, formal, formalism, formula, formulary, function,
   good form, goody-goodness, goody-goodyism, graduation,
   graduation exercises, gravity, grimness, guideline, heraldry,
   holy rite, inaugural, inauguration, inflexibility, initiation,
   institution, jus, law, law of nature, legislation, lex, liturgy,
   long face, maxim, measure, mode of worship, mummery, mystery, norm,
   norma, observance, office, order of nature, order of worship,
   ordinance, ordonnance, overniceness, overpreciseness,
   overrefinement, pedantry, performance, politesse, pomp, practice,
   preciosity, preciousness, precisianism, precision, prescribed form,
   prescript, prescription, pride, principle, procedure, propriety,
   protocol, punctilio, purism, regulation, religious ceremony,
   rigidity, rite, rite de passage, rite of passage, ritual,
   ritual observance, rituality, rubric, rule, ruling, sacrament,
   sacramental, sedateness, seemliness, seriousness, service,
   set form, sober-mindedness, soberness, sobersidedness, sobersides,
   sobriety, social convention, social usage, solemnity,
   solemnization, solemnness, somberness, staidness, standard,
   standing order, state, statute, stiffness, straight face,
   strictness, thoughtfulness, universal law, weightiness, wont



Bouvier's Law Dictionary, Revised 6th Ed (1856):

FORMALITY. The conditions which must be observed in making contracts, and
the words which the law gives to be used in order to render them valid; it
also signifies the conditions which the law requires to make regular
proceedings.