Definify.com
Webster 1913 Edition
Demonstrative
De-mon′stra-tive
,Adj.
 [F. 
démonstratif
, L. demonstrativus
.] 1. 
Having the nature of demonstration; tending to demonstrate; making evident; exhibiting clearly or conclusively. 
“Demonstrative figures.” Dryden.
 An argument necessary and 
demonstrative
. Hooker.
2. 
Expressing, or apt to express, much; displaying feeling or sentiment; 
as, her nature was 
. demonstrative
3. 
Consisting of eulogy or of invective. 
“Demonstrative eloquence.” Blair.
 Demonstrative pronoun 
(Gram.)
, a pronoun distinctly designating that to which it refers.
 De-mon′stra-tive
,Noun.
 (Gram.) 
A demonstrative pronoun; 
as, “this” and “that” are 
. demonstratives
Webster 1828 Edition
Demonstrative
DEMONSTRATIVE
,Adj.
  1.
  Showing or proving by certain evidence; having the power of demonstration; invincibly conclusive; as a demonstrative argument, or demonstrative reasoning.2.
  Having the power of showing with clearness and certainty; as a demonstrative figure in painting.