extraterrestrial

American  

[ek-struh-tuh-res-tree-uhl] / ˌɛk strə təˈrɛs tri əl /

adjective

1. outside, or originating outside, the limits of the earth.

   People on earth have long speculated about the idea of extraterrestrial life.

   Cataclysmic wildfires could be expected if earth were to take an extraterrestrial hit.

---

noun

1. a being originating from beyond the earth; an alien from outer space.

   It was your typical sci-fi novel about extraterrestrials conquering the earth.

extraterrestrial British  

/ ˌɛkstrətɪˈrɛstrɪəl /

adjective

1. occurring or existing beyond the earth's atmosphere

---

noun

1. (in science fiction) a being from beyond the earth's atmosphere

extraterrestrial Scientific  

/ ĕk′strə-tə-rĕs′trē-əl /

1. Originating, located, or occurring outside the Earth or its atmosphere.

---

extraterrestrial Cultural  

1. A descriptive term for things outside the Earth, such as possible civilizations outside the solar system, or objects, such as meteorites, that actually reach the Earth.

---

Other Word Forms

• extraterrestrially
  adverb

Etymology

Origin of extraterrestrial

First recorded in 1865–70; extra- + terrestrial

Explanation

Use the adjective extraterrestrial to describe anything that comes from or exists outside of the earth, like life on a distant planet, material from an asteroid, or even the sun. The word extraterrestrial makes most people think of big-headed green aliens in spaceships, and if you saw one you'd be right to describe it that way. But as both a noun and an adjective, the word is most often used by scientists to talk about anything — life, rocks, or environments on other planets — that happens outside of the earth's atmosphere. This makes sense when you know that in Latin, extra means "outside" and terra means "earth."

Example Sentences

"Extraterrestrial intelligences, ETIs, in our galaxy are probably pretty rare," says Scherf.

From Science Daily • Oct. 12, 2025

According to the European Space Agency, the Einstein Probe is a partnership between the agency, the Chinese Academy of Sciences and the Max Planck Institute for Extraterrestrial Physics.

From BBC • Jan. 9, 2024

Mr. Dawood is also on the board of trustees for the Search for Extraterrestrial Intelligence Institute.

From New York Times • Jun. 19, 2023

On a recent podcast about my book Extraterrestrial, I was asked whether extraterrestrial intelligence should be expected to follow the rational underpinning of morality, as neatly formulated by the German philosopher Immanuel Kant.

From Scientific American • Jul. 12, 2021

Extraterrestrial intelligence will be elegant, complex, internally consistent and utterly alien.

From "Cosmos" by Carl Sagan