The Collaborative International Dictionary of English v.0.48:

Indirect \In`di*rect"\, a. [Pref. in- not + direct: cf. F.
   indirect.]
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   1. Not direct; not straight or rectilinear; deviating from a
      direct line or course; circuitous; as, an indirect road.
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   2. Not tending to an aim, purpose, or result by the plainest
      course, or by obvious means, but obliquely or
      consequentially; by remote means; as, an indirect
      accusation, attack, answer, or proposal.
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            By what bypaths and indirect, crooked ways
            I met this crown.                     --Shak.
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   3. Not straightforward or upright; unfair; dishonest; tending
      to mislead or deceive.
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            Indirect dealing will be discovered one time or
            other.                                --Tillotson.
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   4. Not resulting directly from an act or cause, but more or
      less remotely connected with or growing out of it; as,
      indirect results, damages, or claims.
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   5. (Logic & Math.) Not reaching the end aimed at by the most
      plain and direct method; as, an indirect proof,
      demonstration, etc.
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   Indirect claims, claims for remote or consequential damage.
      Such claims were presented to and thrown out by the
      commissioners who arbitrated the damage inflicted on the
      United States by the Confederate States cruisers built and
      supplied by Great Britain.

   Indirect demonstration, a mode of demonstration in which
      proof is given by showing that any other supposition
      involves an absurdity (reductio ad absurdum), or an
      impossibility; thus, one quantity may be proved equal to
      another by showing that it can be neither greater nor
      less.

   Indirect discourse. (Gram.) See Direct discourse, under
      Direct.

   Indirect evidence, evidence or testimony which is
      circumstantial or inferential, but without witness; --
      opposed to direct evidence.

   Indirect tax, a tax, such as customs, excises, etc.,
      exacted directly from the merchant, but paid indirectly by
      the consumer in the higher price demanded for the articles
      of merchandise.
      [1913 Webster]

WordNet (r) 3.0 (2006):

indirect evidence
    n 1: evidence providing only a basis for inference about the
         fact in dispute [syn: circumstantial evidence, indirect
         evidence] [ant: direct evidence]

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

INDIRECT EVIDENCE. That proof which does not prove the fact in question, but
proves another, the certainty of which may lead to the discovery of the
truth of the one sought.