Definition of "flap"

noun:
- Anything broad and flexible that hangs loose, or that is attached by one side or end and is easily moved.
  
  from Wiktionary, Creative Commons Attribution/Share-Alike License
- A hinged leaf, as of a table or shutter.
  
  from Wiktionary, Creative Commons Attribution/Share-Alike License
- An upset, stir, scandal or controversy.
  
  from Wiktionary, Creative Commons Attribution/Share-Alike License
- The motion of anything broad and loose, or a stroke or sound made with it.
  
  from Wiktionary, Creative Commons Attribution/Share-Alike License
verb:
- To move (something broad and loose) back and forth.
  
  from Wiktionary, Creative Commons Attribution/Share-Alike License