extraterrestrial

extraterrestrial — adjective

1. relating to life or objects that exist or come from somewhere beyond the Earth's

1.adjectiveB2
Definition

relating to life or objects that exist or come from somewhere beyond the Earth's atmosphere.

Example

Dr. Talia Okonkwo detected an extraterrestrial radio signal from a galaxy far beyond our own.

attributive: extraterrestrial radio signal

The research team in Chile studied rock samples that may have an extraterrestrial origin.

attributive: extraterrestrial origin

Common collocations
  • extraterrestrial life
  • extraterrestrial intelligence
  • extraterrestrial origin
  • extraterrestrial signal
  • extraterrestrial being
  • extraterrestrial object
Synonyms
  • alien

    more common in everyday language; can also mean 'foreign' or 'strange', whereas extraterrestrial is specific to outer space

  • cosmic

    broader in scope — refers to the entire universe rather than specifically 'beyond Earth'

  • space-based

    more literal and technical; focuses on location rather than origin

Antonyms
  • terrestrial

    direct opposite — relating to the planet Earth

  • earthly

    emphasises the contrast with 'from space'

Grammar Patterns

extraterrestrial + noun

be + extraterrestrial

Usage Note

Often used attributively before nouns such as life, signal, being, or origin. The predicative use (e.g., 'the object might be extraterrestrial') is less common but acceptable.

Common Mistakes

The scientist found extra-terrestrial life.
The scientist found extraterrestrial life.
the standard spelling has no hyphen, though a few older sources use one.
The building has an extraterrestrial design.' (when meaning unusual or foreign).
The building has a futuristic design.
extraterrestrial should refer specifically to things beyond Earth, not just anything strange.

extraterrestrial — noun

Word family

Synonym discussion

Sense: adjective/1

Alien is the closest everyday synonym for extraterrestrial and is far more common in casual conversation, but it has a broader meaning — it can describe anything strange or foreign, not just things from outer space. Cosmic refers to the entire universe as a whole rather than specifically 'beyond Earth' (e.g., 'cosmic radiation' fills all of space, not just regions beyond Earth). Interplanetary is narrower than extraterrestrial: it describes travel or connections between planets within a solar system, whereas extraterrestrial includes anything from anywhere beyond Earth. Space-based is more literal — it describes technology or objects physically located in space, regardless of origin. For example: an alien spacecraft (common usage), cosmic dust (universal scope), interplanetary travel (Mars to Jupiter), and a space-based telescope (orbiting Earth).

alien ↗cosmic ↗interplanetaryspace-based

Common collocations

Nouns

Phrases

  • search for extraterrestrial intelligence (SETI)
  • extraterrestrial life form

Prepositions

  • extraterrestrial from [a planet / another world]

Etymology

LatinEnglish

Extraterrestrial was formed in English in the mid-20th century (around the early years of the Space Age) by combining three Latin elements: the prefix extra- meaning 'beyond' or 'outside', the noun terra meaning 'Earth' or 'land', and the suffix -estris meaning 'belonging to'. So the word literally means 'belonging to a place beyond Earth.' Though the parts are ancient, the compound is modern — it emerged alongside space exploration and science fiction.