Merriam-Webster's Word of the Day for August 30, 2023 is:

caustic • \KAWSS-tik\  • adjective

In general contexts, caustic describes bluntly and harshly critical remarks, statements, or ways of being and communicating, as in "a caustic remark" or "caustic humor." In contexts involving chemistry, caustic is a synonym of corrosive, and is used to describe things capable of destroying or eating away matter by chemical action.

// She was a writer whose caustic wit endears her still to readers everywhere.

// The chemical was so caustic that it ate through the pipes.

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Examples:

"For [novelist Milan] Kundera, the deadly foe of truthful art was kitsch: the narcissistic sentimentality that, under any social system, effaces realities and encourages people to 'gaze into the mirror of the beautifying lie.' With caustic irony, mordant wit and acrobatic literary skill, he mocked the beautifying lie wherever he found it—in politics, in culture or in personal relationships." — The Economist, 13 July 2023

Did you know?

If you have a burning desire to know the origins of caustic, you're already well on your way to figuring it out. Caustic was formed in Middle English as an adjective describing chemical substances, such as lime and lye, that are capable of destroying or eating away at something. The word is based on the Latin adjective causticus, which itself comes ultimately from the Greek verb kaiein, meaning "to burn." In time, caustic was baked into the English language as an adjective describing people or things (such as wit or remarks) that are bitingly sarcastic. Other kaiein descendants in English include cautery and cauterize, causalgia (a burning pain caused by nerve damage), and encaustic (a kind of paint that is heated after it's applied).