(1):
(v. t.) To turn suddenly, as something broad and flat.
(2):
(v. i.) To strike about with something broad abd flat, as a fish with its tail, or a bird with its wings; to rise and fall; as, the brim of a hat flops.
(3):
(v. i.) To fall, sink, or throw one's self, heavily, clumsily, and unexpectedly on the ground.
(4):
(v. t.) To clap or strike, as a bird its wings, a fish its tail, etc.; to flap.
(5):
(n.) Act of flopping.