In a sharp, harsh, or biting manner that is intended to hurt someone's feelings or make a critical point.
From 'cutting' (sharp, severe) + '-ly' (adverb suffix). The figurative sense of 'cutting' as emotionally sharp dates to Middle English.
When we say someone speaks 'cuttingly,' we're using a metaphor where words are weapons—the same image appears in dozens of languages because getting 'cut' by words feels physically real to the brain.
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