Which word describes someone who is easily irritated or annoyed?

The term that best captures someone who is easily irritated or annoyed is "petulant." This word conveys a sense of peevishness or sulkiness, often associated with a child-like irritability and a tendency to become upset over trivial matters. A petulant person is characterized by a lack of patience and frequent displays of annoyance, making it an apt description for someone who quickly becomes irritated.

In contrast, the other choices indicate different dispositions. "Complacent" refers to a self-satisfied attitude, often without awareness of potential dangers or deficiencies, which does not imply irritability. "Cheerful" describes a happy and optimistic disposition, while "relaxed" suggests a calm and laid-back demeanor. Neither of these choices aligns with the idea of being easily annoyed; rather, they indicate a sense of contentment or ease. Hence, "petulant" is the most fitting choice for a person who frequently exhibits irritation or annoyance.