A capricious person is someone who is unpredictable and impulsive in their behavior, with sudden and unexpected changes in mood or attitude. If you're looking for some synonyms to describe this type of person, you could use terms such as volatile, mercurial, erratic, whimsical, fickle, flighty, unpredictable, or unstable. These words all convey a sense of someone who is difficult to predict or control, and whose actions are often at odds with their previous behavior. Whether you're describing a friend, family member, or colleague, these words can help you capture the essence of a truly capricious person.