(1) Relating to or suffering from indigestion. (2) Having an irritable temperament; ill-humored.
Example:
For decades, the dyspeptic columnist served as the newspaper's -- and the city's -- resident grouch.
Dyspepsia comes from the Greek word for "bad digestion." Interestingly, the Greek verb pessein can mean either "to cook" or "to digest"; a lot of bad cooking has been responsible for a lot of dyspepsia. Dyspepsia can be caused by many diseases, but often dyspeptic individuals are the victims of their own habits and appetites. Worry, overeating, inadequate chewing, and excessive smoking and drinking can all bring on dyspepsia. Today we generally use dyspeptic to mean "irritable" -- that is, in the kind of mood that could be produced by bad digestion.