The term 'WINDY DAY TOY' can be summarized by the four-letter crossword solution 'KITE'. Kites are a traditional toy that have been around for centuries, and they are especially popular on windy days. They are typically made of lightweight materials such as paper or fabric, and are flown in the air with the help of a string attached to a handle. Kites are a fun way to enjoy the outdoors on a windy day.