dis·grun·tle 
(dĭs-grŭntl)
(dĭs-grŭntl)tr.v. dis·grun·tled, dis·grun·tling, dis·grun·tles
To make discontented.
[DIS- + gruntle, to grumble (from Middle English gruntelen, frequentative of grunten, to grunt; see GRUNT).]
dis·gruntle·ment n.