To be “cold blooded” can mean two different things, depending on context:

1. In everyday and moral talk

When people say someone is “cold blooded,” they usually mean the person is emotionally unfeeling and capable of cruel actions without guilt or sympathy.

Common uses:

  • “Cold‑blooded killer” → someone who plans and commits murder calmly and deliberately.
  • “Cold‑blooded decision” → a harsh choice made in a detached, purely logical way, without compassion.
  • “In cold blood” → doing something violent or cruel on purpose, with a clear head, not in the heat of passion.

Key idea: the person is seen as:

  • Calm and controlled on the outside.
  • Lacking warmth, empathy, or remorse.
  • Willing to hurt others if it serves their goal.

This sense comes from an older belief that strong emotions “heat” the blood, so “cold blood” = no emotion.

2. In biology and animals

“Cold‑blooded” is also a scientific-ish term for animals whose body temperature depends on the environment (more precisely: ectothermic).

  • Examples: fish, snakes, lizards, amphibians like frogs.
  • When it is warm and sunny, they warm up; when it is cool, they cool down.
  • They’re not sluggish all the time; many can be very active as soon as conditions are right.

Important: a “cold‑blooded” animal is not morally cold; that’s just how its body works.

Mini summary (TL;DR)

  • In human behavior, “cold blooded” = calm, deliberate, and cruel, with little or no empathy or remorse.
  • In biology, “cold‑blooded” = an animal whose body temperature follows the surrounding air or water.

Information gathered from public forums or data available on the internet and portrayed here.