mutton flaps Posted in M Best definition mutton flaps Slang term for labia, the lips around a womanÃ¢ÂÂs vagina. Her mutton flaps were so long, she could probably spread her flaps and fly. How satisfied are you with the definition? Looking for mutton flaps meaning? Delighted that you discovered the greatest determine on our web site! Recently this definition was actually observed 108 times.