Splenetic describes someone who is bad-tempered in a sour, bitter way, or the writing and speech of such a person — a splenetic old man, a splenetic letter to the newspaper, a splenetic attack on the government. It is not the hot anger that flares and passes; it is the cold, long-running kind, full of complaint and ill will. The word is formal and literary. You will meet it in book reviews, opinion columns, and novels; nobody says it in an ordinary conversation, and if you used it while chatting with friends it would sound very bookish. It comes from an old idea about the body: doctors long ago believed that four fluids ran through us and set our moods, and that the spleen — an organ near the stomach — produced the one that made people angry and gloomy. The medicine was wrong, but the language kept it. That is why we still say someone 'vents their spleen' when they let their anger out. There is a rare noun use for such a person, but you will almost always meet the adjective.

暴躁易怒的、滿腹牢騷的（帶著怨氣的那種脾氣壞，不是一時火大）