The word "shirty" is often used to describe someone who is irritable or easily annoyed. There are plenty of other synonyms that can be used to describe a person's temperamental behavior. These include words like grumpy, testy, snappish, peevish, surly, cranky, irascible, petulant, and moody. All of these words describe someone who is easily angered and prone to sudden outbursts or mood swings. While the word "shirty" may not be commonly used in everyday conversation, it is the perfect way to describe someone who is easily irritable and difficult to deal with.