v. To make discontent or cross; to cause being in a bad temper.
the GNU version of the Collaborative International Dictionary of English
v. To dissatisfy; to disaffect; to anger.
The Century Dictionary and Cyclopedia
To disappoint; disconcert; chagrin; disgust; offend; throw into a state of sulky dissatisfaction: usually in the participial adjective disgruntled.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
v. put into a bad mood or into bad humour
Word Usage
"Your problem with the word disgruntle the problem being that it seems to mean pretty much the same as gruntle doesn’t take into consideration the pig factor."