thrash
v.v. to hit something or someone very hard many times, often with a stick. It can also mean to move your arms and legs around in a wild or uncontrolled way.
v. to beat soundly or strike repeatedly with a whip or stick; also describes the act of moving limbs about violently or spasmodically.
The swimmer started to thrash his arms in the water.
The angry waves caused the small boat to thrash against the wooden pier until the ropes finally snapped.
In his feverish state, the patient began to thrash about so violently that the nurses had to move the bedside equipment to prevent him from injuring himself.
From Middle English thrasshen, a dialectal variant of thresshen, threshen (whence the modern English thresh), from Old English þrescan, from Proto-Germanic *þreskaną, whence also Old High German dreskan, Old Norse þreskja.
The verb is transitive when meaning to beat something, but often intransitive when describing wild movement, frequently followed by 'about' or 'around'.
he was thrashing his legs about the bedhe was thrashing his legs about on the bedWhen describing wild movement in a location, 'thrash about' requires a preposition like 'on' or 'in' to connect to the place.