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

• affectless
• callous
• case-hardened
• cold-blooded
• compassionless
• desensitized
• hard
• hard-boiled
• hard-hearted
• heartless
• indurate
• inhuman
• inhumane
• insensate
• insensitive
• ironhearted
• obdurate
• pachydermatous
• pitiless
• remorseless
• ruthless
• slash-and-burn
• soulless
• stony
• stoney
• stonyhearted
• take-no-prisoners
• thick-skinned
• uncharitable
• unfeeling
• unmerciful
• unsparing
• unsympathetic

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

Inspired by Lauren’s late mother, Adele, who was diagnosed with early-onset Alzheimer’s at the age of 55, their family knows that this merciless disease is no laughing matter. —Jeff Conway, Forbes.com, 17 Apr. 2025

Lottie proposes that Natalie be stripped of her title and that the merciless and vicious Shauna should lead them instead. —Erin Qualey, Vulture, 14 Mar. 2025

The animal is fully present, merciless and hungry. —Sara Holdren, Vulture, 11 Mar. 2025

In the series' latest episode, released March 9, Alex arrives to Ellis Island after a treacherous few weeks at sea, only to be put through even more turmoil as she's subjected to a series of invasive medical examinations by three merciless male doctors. —Julia Moore, People.com, 10 Mar. 2025

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