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

That kind of global spending sounds good but what about extraterrestrial spending?

From Barron's • Mar. 30, 2026

The findings suggest that RNP condensates could serve as biomarkers, or biological indicators, of cellular stress in extraterrestrial environments.

From Science Daily • Feb. 8, 2026

When this extraterrestrial jetsam occasionally plunges through the atmosphere, it poses a risk to life, infrastructure and the environment.

From The Wall Street Journal • Jan. 23, 2026

Her creations give nods to nature, at times skew extraterrestrial, and have Afro-futuristic undertones.

From Los Angeles Times • Dec. 30, 2025

“Fascinating. What do you think would be humanity’s reaction if we ever really discovered extraterrestrial life?”

From "The Smartest Kid in the Universe" by Chris Grabenstein