In a sharp, cutting, or sarcastic manner; with a tone or quality that stings or hurts emotionally or physically.
From 'biting' (present participle of 'bite', Old English 'bitan') plus the adverbial suffix '-ly'. The figurative sense of 'biting' meaning sharp or cutting evolved from the physical sensation of teeth breaking skin.
Language can bite just as painfully as teeth—when someone makes a 'bitingly sarcastic' comment, they're using words as weapons, and interestingly, research shows that emotional wounds from harsh speech can activate the same brain regions as physical pain.
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