The Collaborative International Dictionary of English v.0.48:

Demonstrative \De*mon"stra*tive\, a. [F. d['e]monstratif, L.
   demonstrativus.]
   1. Having the nature of demonstration; tending to
      demonstrate; making evident; exhibiting clearly or
      conclusively. "Demonstrative figures." --Dryden.
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            An argument necessary and demonstrative. --Hooker.
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   2. Expressing, or apt to express, much; displaying feeling or
      sentiment; as, her nature was demonstrative.
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   3. Consisting of eulogy or of invective. "Demonstrative
      eloquence." --Blair.
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   Demonstrative pronoun (Gram.), a pronoun distinctly
      designating that to which it refers.
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WordNet (r) 3.0 (2006):

demonstrative pronoun
    n 1: a pronoun that points out an intended referent [syn:
         demonstrative pronoun, demonstrative]