noun
beating; beating up
Colloquial term for physically beating someone up; used in rough or casual contexts.
あいつにひどいおさ打ちを食らわせた。
I gave that guy a severe beating.
殴打 is a formal or legal term for striking or battery, while おさ打ち is slangy and implies a rough, informal beating.
ぼこぼこにする is a common colloquial expression for beating someone up thoroughly, similar in register to おさ打ち.
The origin is uncertain. The first element おさ may be a dialectal or slang term, possibly related to 筬 (reed) used metaphorically for a beating tool, but this is speculative. The word is not standard and appears in limited contexts.