The term 'IN A PET' can be broken down into four words, each of which describes a feeling of anger or frustration. PEEVED is a six-letter word meaning to be irritated or annoyed. IRED is a four-letter word meaning to be angry or resentful. SORE is also a four-letter word meaning to be hurt or upset. HETUP is a five-letter word meaning to be agitated or riled up. All of these words describe feelings of anger or frustration that can be experienced when someone is in a pet.