noun
A retaliatory strike or counterattack, often used in boxing, martial arts, or figurative contexts.
彼は相手のパンチをかわして強烈なカウンターブロウを決めた。
He dodged his opponent's punch and landed a powerful counterblow.
カウンター is a broader term for 'counter' in various contexts (counterattack, countermeasure, counter in a store, etc.), while カウンターブロウ specifically refers to a counterblow or counterpunch.
Loanword from English 'counterblow'.