The term 'Ballet Bird' is a reference to the iconic role of the SWAN in classical ballet. The word 'SWAN' is a four-letter word that can be used to complete the crossword solution. The SWAN is a graceful and elegant creature that has been used as a symbol of beauty and grace in many cultures for centuries. In classical ballet, the SWAN is often used to represent a female character, usually a princess or a queen. The SWAN is also a popular figure in literature, art, and music, and is often used to represent love, loyalty, and purity.