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.

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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

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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.

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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.

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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

Geochemical testing of the stromatolites revealed signs of both extraterrestrial material and nearby bedrock, along with evidence that the structures were altered by hot water.

From Science Daily • May 22, 2026

His latest brings extraterrestrial life into the realm of ’70s conspiracy thrillers.

From Los Angeles Times • May 14, 2026

The US has seen renewed public interest in extraterrestrial life in recent years.

From BBC • May 8, 2026

The Pentagon on Friday released a first batch of secret files documenting reported sightings of unidentified flying objects -- some dating back to the 1940s -- fanning speculation over whether extraterrestrial life exists.

From Barron's • May 8, 2026

How would we explain the global arms race to a dispassionate extraterrestrial observer?

From "Cosmos" by Carl Sagan