The term 'mythical flapper' is a crossword solution that can be completed with the three-letter word 'ROC'. A ROC is a mythical bird of enormous size and strength that appears in the folklore of many cultures. It is often described as an eagle-like creature, capable of carrying off large animals such as elephants. In some stories, it is said to have the power to cause storms and other natural disasters. The ROC is a popular figure in fantasy literature, appearing in works such as One Thousand and One Nights and The Lord of the Rings.