flail
1. [ verb ] give a thrashing to; beat hard
Synonyms: thrash lam thresh
Related terms: beat bat
2. [ noun ] an implement consisting of handle with a free swinging stick at the end; used in manual threshing
Related terms: implement thrash
3. [ verb ] move like a flail; thresh about
Synonyms: thresh
Examples:

"Her arms were flailing"

Related terms: beat