flail
Definitions
To wave or swing or cause to wave or swing wildly.
To thrash about or struggle uselessly.
A threshing tool consisting of a wooden staff with a short heavy stick swinging from it.
Examples
The drowning man began to flail his arms in a desperate attempt to stay above the water.
The scarecrow's tattered sleeves started to flail wildly in the gusty wind.
Without any clear direction, the team began to flail and lose their momentum during the project.