Which word would you use to describe a very irritable person?

The term 'splenetic' is particularly well-suited to describe a very irritable person because it comes from an older belief that the spleen was associated with emotions such as anger and irritation. Therefore, someone who is splenetic exhibits a disposition marked by bad temper or irritability. This word captures the essence of a person who is prone to fits of anger or annoyance, thus making it the most accurate choice when describing irritability.

In contrast, 'stentorian' refers to an extremely loud voice, 'salacious' is related to lust or a lewd nature, and 'sophomoric' describes someone who is immature or overconfident, particularly in their knowledge or approach to situations. None of these words convey the specific quality of irritability that 'splenetic' encapsulates.