In a way that makes something worse or more annoying; in an aggravating manner.
From exacerbate (Latin ex- 'out' + acerbus 'sour, harsh') + -ing + -ly. The root acerbus refers to sour or bitter taste, which evolved metaphorically to mean making conditions more severe or irritating.
The word 'acerbus' originally described sour wine, but Romans used it to describe harsh situations—showing how our taste buds gave us vocabulary for emotional bitterness that we still use today.
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