dyspeptic

The word "dyspeptic" began with physical discomfort, but it also grew into a word for a certain kind of temperament. In its literal sense, it means suffering from dyspepsia: indigestion or poor digestion. Someone who feels bloated, uneasy, or sick after eating could be described as dyspeptic.

From there, the word naturally took on a figurative sense. A person in stomach distress may be cross and uncomfortable, so "dyspeptic" also came to describe someone who is habitually bad-tempered, irritable, gloomy, or hard to please. In this sense, it often suggests a sour, complaining manner or a habit of finding fault in everything.

It is usually stronger than saying someone is merely in a bad mood for a moment. A dyspeptic person seems settled into that sour frame of mind. You might describe a harsh reviewer as dyspeptic if they dismiss every book with a sneer, or say that an old professor has a dyspeptic view of modern art if he greets every new idea with gloom and irritation.

In modern writing, the figurative sense is often more common than the medical one, but both are still valid. The older link to indigestion helps explain the flavor of the word: it suggests inner discomfort showing itself as outward sourness. So whether you are talking about an upset stomach or a person with a sharp, gloomy, complaining manner, "dyspeptic" is the right word.