The Collaborative International Dictionary of English v.0.48:

Circumstantial \Cir`cum*stan"tial\, n.
   Something incidental to the main subject, but of less
   importance; opposed to an essential; -- generally in the
   plural; as, the circumstantials of religion. --Addison.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

circumstantial \cir`cum*stan"tial\ (s[~e]r`k[u^]m*st[a^]n"shal),
   a. [Cf. F. circonstanciel.]
   [1913 Webster]
   1. Consisting in, or pertaining to, circumstances or
      particular incidents.
      [1913 Webster]

            The usual character of human testimony is
            substantial truth under circumstantial variety.
                                                  --Paley.
      [1913 Webster]

   2. Incidental; relating to, but not essential.
      [1913 Webster]

            We must therefore distinguish between the essentials
            in religious worship . . . and what is merely
            circumstantial.                       --Sharp.
      [1913 Webster]

   3. Abounding with circumstances; detailing or exhibiting all
      the circumstances; minute; particular.
      [1913 Webster]

            Tedious and circumstantial recitals.  --Prior.
      [1913 Webster]

   Circumstantial evidence (Law), evidence obtained from
      circumstances, which necessarily or usually attend facts
      of a particular nature, from which arises presumption.
      According to some authorities circumstantial is
      distinguished from positive evidence in that the latter is
      the testimony of eyewitnesses to a fact or the admission
      of a party; but the prevalent opinion now is that all such
      testimony is dependent on circumstances for its support.
      All testimony is more or less circumstantial. --Wharton.

   Syn: See Minute.
        [1913 Webster]

WordNet (r) 3.0 (2006):

circumstantial
    adj 1: fully detailed and specific about particulars; "a
           circumstantial report about the debate"

Moby Thesaurus II by Grady Ward, 1.0:

124 Moby Thesaurus words for "circumstantial":
   absolute, accessory, accidental, accompanying, accurate,
   additional, adducible, admissible, ado, adscititious, adventitious,
   afloat, afoot, aleatory, appurtenant, ascititious, attestative,
   attestive, authentic, auxiliary, based on, blow-by-blow, casual,
   certain, chance, close, collateral, complete, conclusive,
   conditional, contingent, convincing, cumulative, current, damning,
   decisive, deduced, detailed, determinative, documentary,
   documented, doing, eventuating, evidential, evidentiary, ex parte,
   exact, explicit, extra, extraneous, eye-witness, factual, final,
   firsthand, fortuitous, founded on, full, going on, grounded on,
   happening, hearsay, implicative, implicit, implied, in hand,
   in the wind, incidental, incontrovertible, indicative, indirect,
   indisputable, inessential, inferential, inferred, interpretive,
   irrefutable, irresistible, itemized, material, minute, nice,
   nonessential, nuncupative, occasional, occurring, on, on foot,
   ongoing, overwhelming, particular, particularized, passing,
   precise, presumable, presumed, presumptive, prevailing, prevalent,
   probative, provisional, reliable, replete, resultant, secondary,
   significant, specific, strict, subsidiary, suggestive, superadded,
   superfluous, supervenient, supplemental, supplementary, sure,
   symptomatic, taking place, telling, thorough, under way,
   unessential, unimportant, valid, weighty