The word 张牙舞爪 is formed by combining two parallel verb-object constructions: 张牙, where 张 means "to open" or "bare" and 牙 means "teeth", and 舞爪, where 舞 means "to brandish" or "wave" and 爪 means "claws". These four characters are joined in a fixed sequence to create an idiom that literally depicts the actions of baring teeth and waving claws, directly illustrating aggressive behavior.