The Collaborative International Dictionary of English v.0.48:

Demonstrative \De*mon"stra*tive\, n. (Gram.)
   A demonstrative pronoun; as, "this" and "that" are
   demonstratives.
   [1913 Webster]

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.
      [1913 Webster]

            An argument necessary and demonstrative. --Hooker.
      [1913 Webster]

   2. Expressing, or apt to express, much; displaying feeling or
      sentiment; as, her nature was demonstrative.
      [1913 Webster]

   3. Consisting of eulogy or of invective. "Demonstrative
      eloquence." --Blair.
      [1913 Webster]

   Demonstrative pronoun (Gram.), a pronoun distinctly
      designating that to which it refers.
      [1913 Webster]

WordNet (r) 3.0 (2006):

demonstrative
    adj 1: given to or marked by the open expression of emotion; "an
           affectionate and demonstrative family" [ant:
           undemonstrative]
    2: serving to demonstrate [syn: demonstrative, illustrative]
    n 1: a pronoun that points out an intended referent [syn:
         demonstrative pronoun, demonstrative]

Moby Thesaurus II by Grady Ward, 1.0:

162 Moby Thesaurus words for "demonstrative":
   Christophanic, Satanophanic, accessible, adoring, affectional,
   affectionate, affective, allegorizing, angelophanic, annotative,
   apodictic, appearing, approachable, candid, clarifying,
   communicative, conjugal, connotative, conversable, critical,
   demonstrating, demonstrational, demythologizing, denominative,
   denotative, designative, devoted, diagnostic, disclosive,
   displaying, editorial, effusive, elucidative, emblematic,
   emotiometabolic, emotiomotor, emotional, emotiovascular, emotive,
   enlightening, epiphanic, euhemeristic, evident, evidential,
   evincive, exegetic, exemplificative, exhibitive, expansive,
   explaining, explanatory, explicative, explicatory, expositional,
   expositive, expository, expressive, extroverted, faithful, feeling,
   figural, figurative, filial, fond, frank, free, free-speaking,
   free-spoken, free-tongued, glandular, glossarial, gossipy, gut,
   husbandly, identifying, ideographic, idiosyncratic, illuminating,
   illuminative, illustrative, implicative, incarnating,
   incarnational, indicating, indicative, indicatory, individual,
   languishing, lovelorn, lovesick, lovesome, loving, manifestative,
   materializing, maternal, meaningful, melting, metaphorical, naming,
   newsy, of soul, open, outgoing, outpouring, outspoken,
   overdemonstrative, parental, paternal, pathognomonic, peculiar,
   plain, pneumatophanic, presentational, probative, profuse,
   promulgatory, provable, rationalistic, rationalizing,
   representative, revelational, revelatory, romantic, scholiastic,
   self-revealing, self-revelatory, semantic, semiotic, sentimental,
   showing, signalizing, significant, significative, signifying,
   sociable, soft, soulful, suggestive, symbolic, symbolistic,
   symbological, symptomatic, symptomatologic, talkative, tender,
   theophanic, typical, unconstrained, unhampered, unrepressed,
   unreserved, unrestrained, unrestricted, unreticent, unsecretive,
   unshrinking, unsilent, unsuppressed, uxorious, visceral, warm,
   wifely