cold-blooded

cold-blooded — adjective

1. describing animals and other creatures whose internal warmth matches the world a

1.adjectiveB2
Definition

describing animals and other creatures whose internal warmth matches the world around them, rather than being generated from inside — applies to reptiles, fish, amphibians, and insects

Example

Since snakes are cold-blooded, they need sunlight to warm up before they can hunt.

topic: animal biology; predict + result clause

The biology teacher told the class that all reptiles are cold-blooded creatures.

attributive use: cold-blooded + creature

Common collocations
  • cold-blooded animals
  • cold-blooded creatures
  • cold-blooded reptiles
  • cold-blooded species
Synonyms
  • ectothermic

    the formal scientific term; very rare in everyday speech

  • poikilothermic

    a highly technical synonym used mainly in zoology textbooks

Antonyms
  • warm-blooded

    the direct opposite; used for mammals and birds that maintain a steady internal body temperature

Grammar Patterns

cold-blooded + noun (animal type)

be + cold-blooded

Usage Note

This is a neutral scientific term for animals. Using 'cold-blooded' to describe a person who feels cold is not standard English and may be misunderstood as an insult.

Common Mistakes

My cat is cold-blooded so she sleeps in the sun.
My cat loves sleeping in the sun like many animals, but cats are actually warm-blooded.
The biological sense applies only to reptiles, amphibians, fish, and insects; mammals are warm-blooded.

2. done with complete cruelty and without any feeling of guilt or pity — for exampl

2.adjectiveB2
Definition

done with complete cruelty and without any feeling of guilt or pity — for example, a planned murder of an innocent person, or a heartless decision that causes great suffering

Example

The killer was found guilty of a cold-blooded murder that shocked the whole neighbourhood.

attributive: cold-blooded + murder

The general ordered a cold-blooded attack on unarmed villagers during the war.

collocation: cold-blooded attack

Common collocations
  • cold-blooded murder
  • cold-blooded killer
  • cold-blooded attack
  • cold-blooded decision
  • cold-blooded act
Synonyms
  • ruthless

    similar intensity but focuses on achieving a goal without caring who gets hurt; less tied to violent crime

  • merciless

    emphasises the refusal to show any mercy to someone who is helpless

  • heartless

    slightly less formal; describes a person who lacks kindness or sympathy

  • callous

    focuses on emotional indifference rather than active cruelty

Antonyms
  • compassionate

    showing deep concern for others' suffering

  • kind

    a general positive opposite at a gentler intensity

  • merciful

    showing forgiveness or leniency, the direct opposite of merciless

Grammar Patterns

cold-blooded + noun (murder / killer / attack / decision)

be + cold-blooded (of a person)

Usage Note

This figurative sense is much stronger than words like 'unkind' or 'mean.' It implies a chilling absence of normal human emotion and is most often used for violent crimes or ruthless business decisions. The biological and figurative senses share no overlap in usage — context (human vs. animal) tells the reader which meaning is intended.

Common Mistakes

She was cold-blooded when she forgot my birthday.
She was thoughtless when she forgot my birthday.
'Cold-blooded' is too strong for minor offences; it suggests deliberate cruelty, not carelessness.

Word family

  • cold-bloodedly
    adverbC1
  • cold-bloodedness
    nounC1

Synonym discussion

Sense: adjective/2

All four words describe a lack of kindness or pity, but they differ in intensity and context. 'Cold-blooded' is the most chilling term — it suggests that the person feels no normal human emotion at all, as if they were biologically incapable of sympathy. It is most common in descriptions of violent crime ('cold-blooded murder'). 'Ruthless' focuses on a determined pursuit of goals without caring about harm to others; it often appears in business or political contexts ('a ruthless negotiator'). 'Merciless' highlights the refusal to show mercy to someone already at a disadvantage ('a merciless beating'). 'Heartless' is more everyday and slightly less severe — it describes a general lack of kindness or empathy ('a heartless remark'). 'Callous' emphasises emotional indifference rather than active cruelty; a callous person simply does not care, whereas a cold-blooded one may actively cause harm. For example, a callous boss ignores staff concerns, while a cold-blooded boss fires workers the day before Christmas without a second thought.

ruthlessmercilessheartless ↗callous

Common collocations

Nouns

Adverbs

  • cold-bloodedly

Phrases

Etymology

Old EnglishEnglish

Formed from 'cold' (Old English 'cald' meaning 'having a low temperature') + 'blooded' (from 'blood', Old English 'blōd'). The literal biological sense — describing animals whose body temperature matches their surroundings — appeared in English scientific writing around the 1600s. By the early 1800s, the term had developed a figurative meaning: a person whose emotional coldness resembles the lifeless temperature of a reptile, showing no warmth of human feeling.