The word "petulant" is an adjective that describes a person who exhibits anger or annoyance, typically for trivial reasons. It is often used in a disparaging manner when applied to an adult who is perceived as acting like a child.
Petulance is an attitude that is usually associated with children who throw temper tantrums when they don't get what they want. When the word is applied to an adult, the element of child-like irrationality carries over, making it an insulting way to imply the immaturity of an adult's behavior. Synonyms for the word "petulant" include "peevish" and "irascible," and a proper use of the word in a sentence includes, "Cindy's petulant ranting at the waiter about the lack of a red wine option embarrassed her date."