(1):

(a.) Expressing, or apt to express, much; displaying feeling or sentiment; as, her nature was demonstrative.

(2):

(a.) Consisting of eulogy or of invective.

(3):

(n.) A demonstrative pronoun; as, "this" and "that" are demonstratives.

(4):

(a.) Having the nature of demonstration; tending to demonstrate; making evident; exhibiting clearly or conclusively.