merciless
Americanadjective
adjective
Other Word Forms
Etymology
Origin of merciless
First recorded in 1300–50; Middle English mercyles; see mercy, -less
Explanation
Use the adjective merciless to describe someone who acts in a cruel, heartless way. You could accuse your rabbit-hunting brother of being merciless. Merciless is the antonym, or opposite, of "merciful." If a person shows no mercy or pity, she is merciless. This can describe a cruelly violent person, or it can be more figurative: "The torrential rain was merciless, pouring down on the wedding party as they ran to take cover." The root word is mercy, which comes from the French merci, "reward, gift, or kindness."
Vocabulary lists containing merciless
Hamilton
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Schooled
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Theodore Roosevelt on "The Man with the Muck Rake" (1906)
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Zverev was also undone in last year's Australian Open final by Sinner, who produced a merciless performance which led to the German saying he felt mentally "empty" a few months later.
From BBC ● Jun. 5, 2026
The journalist James Agee’s merciless portraits of his subjects remind Mr. Frazier of “those old-time operations that were done on a kitchen table without anesthetic.”
From The Wall Street Journal ● Jan. 23, 2026
The 1972 peak was followed by a merciless recession in the mid-1970s, and a heartbreaking stock market bust.
From Barron's ● Dec. 31, 2025
Unlike, for example, Molly Jong-Fast’s merciless “How to Lose Your Mother,” “Bad Bad Girl” doesn’t read like a hit job.
From Los Angeles Times ● Oct. 17, 2025
But this time, she’s merciless and doesn’t let go.
From "Free Lunch" by Rex Ogle
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
