merciless

adjective

mer·​ci·​less ˈmər-si-ləs 

: having or showing no mercy : pitiless

the merciless killing of innocent people

mercilessly adverb

mercilessness noun

Synonyms of merciless

• ruthless
• stony

Examples of merciless in a Sentence

the merciless killing of innocent people

He has been merciless in his criticism of his opponent.

Recent Examples on the Web

Regehr was relentless and merciless, and Oilers fans had to witness it over and over again. — Sean McIndoe, New York Times, 25 July 2026

The red card was rescinded; the team was unmoored; conspiracies grew overnight, like mushrooms; and a merciless Belgium swept in and trampled, 4–1, on what remained. — Anthony Lane, New Yorker, 17 July 2026

Soon enough, Karl’s seemingly foolproof blackmail scheme devolves into a merciless, dog-eat-dog fight for survival, and the two men are locked in a cutthroat collision course, their fates now inextricably linked. — Ryan Lattanzio, IndieWire, 15 July 2026

Tis hard to see the mighty prancing war horse, trampling the dying and dead beneath their merciless feet. — Rose Horowitch, The Atlantic, 8 July 2026

Word History

First Known Use

14th century, in the meaning defined above

Rhymes for merciless

• transversalis

Kids Definition

merciless

adjective

mer·​ci·​less ˈmər-si-ləs 

: having no mercy : pitiless

merciless slaughter

mercilessly adverb

mercilessness noun