Flop To strike or turn suddenly ( with something broad and flat ), for example like a fish tail when the fish move its tail / or when suddenly it move and change it direction ,( it called flop ) also , the birds with its wings when they rise and fall ( it called flop too )

When you catch a fish and put it on the ground it flops around.

There's a loose bendy feeling when you use "flop". As though the fish has fallen over and landed loosely. It's impossible to be rigid, and flop at the same time.

flop: to change suddenly, as from one side or party to another