Dyspeptic
Definition: gloomy, pessimistic, irritable
This comes from the word “dyspepsia,” which refers to digestive problems like heartburn and acid reflux.
Presumably, people suffering from dyspepsia are known to be irritable.
Why I Looked It Up
An obituary of the actor Michael Constantine said:
[He was] known as the genially dyspeptic school principal on the popular TV series “Room 222” and, 30 years later, as the genially dyspeptic patriarch in the hit film “My Big Fat Greek Wedding” …