Flappy can be defined as something flexible and unstable, or something that flutters or vibrates rapidly. Synonyms for flappy include floppy, loose, limp, soft, droopy, flimsy, pliable and unsteady. The word flappy is often used to describe loose and unstable objects, such as feathers, wings and clothing. Additionally, it can also be used to describe a certain type of mobile game that features a bird flapping its wings to avoid obstacles. Alternatives to the word flappy can help add variety and nuance to language and make writing more interesting and engaging.