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

More than 3,000 shows and a sizable cult following later, The Dark Room has evolved into a choose-your-own-adventure live action video game, presided over by Robertson as its obscene, merciless and incredibly quick-witted host. — Rebecca Rosman, NPR, 31 Aug. 2026

In Braun’s script, the merciless obstacle course of singlehood seems just absurd. — Faith Hill, The Atlantic, 14 Aug. 2026

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The red card was rescinded; the team was unmoored; conspiracies grew overnight, like mushrooms; and a merciless Belgium swept in and trampled, 4–1, on what remained.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

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