The Collaborative International Dictionary of English v.0.48:

Expostulation \Ex*pos`tu*la"tion\, n. [L. expostulatio.]
   The act of expostulating or reasoning with a person in
   opposition to some impropriety of conduct; remonstrance;
   earnest and kindly protest; dissuasion.
   [1913 Webster]

         We must use expostulation kindly.        --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

expostulation
    n 1: the act of expressing earnest opposition or protest [syn:
         expostulation, remonstrance, remonstration,
         objection]
    2: an exclamation of protest or remonstrance or reproof

The Devil's Dictionary (1881-1906):

EXPOSTULATION, n.  One of the many methods by which fools prefer to
lose their friends.