alien

1 of 3

adjective

ˈā-lē-ən 

ˈāl-yən

1

a

: belonging or relating to another person, place, or thing : strange

an alien environment

b

: relating, belonging, or owing allegiance to another country or government : foreign

alien residents

c

: exotic sense 1

alien plants

d

: coming from another world : extraterrestrial

alien beings

an alien spaceship

When it comes to knowing what alien life forms might be like, we don't have any idea.

—Kate Shuster

2

: differing in nature or character typically to the point of incompatibility

ideas alien to democracy

alienly adverb

alienness

ˈā-lē-ən-nəs 

ˈāl-yən-nəs

noun

alien

2 of 3

noun

1

a

: a person who is not of a particular group or place

aliens seeking asylum in the U.S.

In this way it came to pass that those scattered linen-weavers—emigrants from the town into the country—were to the last regarded as aliens by their rustic neighbours …

—George Eliot

… she whom we had deemed so … pious, at last died an alien from the church …

—Delia Salter Bacon

b

: a foreign-born resident who has not been naturalized and is still a subject or citizen of a foreign country

broadly : a foreign-born citizen

2

: extraterrestrial

a movie about an invasion of Earth by monstrous aliens

3

: exotic sense 1

Russian thistle, kudzu, and other aliens

alien

3 of 3

verb

aliened; aliening; aliens

transitive verb

1

: alienate, estrange

2

: to transfer the title of (property)

Synonyms

Adjective

• foreign

Verb

• anger
• sour
• infuriate
• alienate
• estrange
• outrage

Choose the Right Synonym for alien

extrinsic, extraneous, foreign, alien mean external to a thing, its essential nature, or its original character.

extrinsic applies to what is distinctly outside the thing in question or is not contained in or derived from its essential nature.

sentimental value that is extrinsic to the house's market value

extraneous applies to what is on or comes from the outside and may or may not be capable of becoming an essential part.

arguments extraneous to the issue

foreign applies to what is so different as to be rejected or repelled or to be incapable of becoming assimilated.

techniques foreign to French cuisine

alien is stronger than foreign in suggesting opposition, repugnance, or irreconcilability.

a practice totally alien to her nature

Examples of alien in a Sentence

Adjective

they were careful to learn of any alien business customs before trying to expand overseas

it's completely alien to her nature to wish evil of anyone

Noun

aliens seeking asylum in the U.S.

He claims that he was captured by space aliens.

Verb

such angry outbursts will rapidly alien any friends you might possibly have left

the couple plans to alien the adjoining house lot to their eldest son

Recent Examples on the Web

Adjective

He is charged with conspiring with others to engage in alien smuggling, four counts of alien smuggling for profit, and four counts of alien smuggling resulting in death. —Louis Casiano, FOXNews.com, 1 July 2025

Then Grace encounters an alien ship and a new life form. —ArsTechnica, 30 June 2025

Noun

Mejia-Flores was identified as a fugitive alien with a Final Order of Removal. —Billal Rahman, MSNBC Newsweek, 23 June 2025

Heading into the weekend, the otherworldly tale about a young boy who connects with aliens after getting mistaken for Earth’s intergalactic ambassador was aiming for $25 million to $30 million. —Rebecca Rubin, Variety, 22 June 2025

Verb

In ever more apocalyptic language, Trump has sought to unify his MAGA movement with strongman pledges to defend Americans from millions of hostile foreigners seeking to storm the country and to root out enemy aliens within. —Julia Preston, Foreign Affairs, 25 Oct. 2024

The film follows a ragtag group of actors (played by Tim Allen, Sigourney Weaver, Alan Rickman, among other stars) from an ‘80s sci-fi series who aliens unexpectedly abduct during a convention appearance. —Matt Juul, BostonGlobe.com, 7 July 2023

Word History

Etymology

Adjective

Middle English, "foreign," borrowed from Anglo-French, borrowed from Latin aliēnus "not one's own, of others, foreign, strange," derivative of alius "other" (perhaps going back to *aliai-nos, from an adverbialized locative derivative *aliai "elsewhere") — more at else

Noun

Middle English, "foreigner, outsider," borrowed from Anglo-French, borrowed from Latin aliēnus "slave belonging to another person, foreigner, stranger," noun derivative of aliēnus, adjective, "not one's own, foreign" — more at alien entry 1

Verb

Middle English alienen "to transfer or surrender property rights, exclude," borrowed from Anglo-French aliener (Middle French, "to estrange, deprive of reason"), borrowed from Latin alienāre "to transfer (goods, property), lose possession of, render hostile" — more at alienate

First Known Use

Adjective

14th century, in the meaning defined at sense 1a

Noun

14th century, in the meaning defined at sense 1a

Verb

14th century, in the meaning defined at sense 1

Phrases Containing alien

• anti-alien
• illegal alien
• illegal alien/immigrant
• nonresident alien

Rhymes for alien

• bacchanalian
• episcopalian
• mammalian

Kids Definition

alien

1 of 2 adjective

ˈā-lē-ən 

ˈāl-yən

1

: relating or belonging to another country : foreign

alien residents

2

: exotic sense 1

3

: wholly different in nature or character

opinions alien to his outlook

4

: belonging or relating to another person, place, or thing : strange

5

: coming from another world : extraterrestrial

alien

2 of 2 noun

1

: a resident who was born elsewhere and is not a citizen of the country in which he or she now lives

2

: a being that comes from or lives in another world : extraterrestrial

3

: exotic

Legal Definition

alien

1 of 3 adjective

ˈā-lē-ən, ˈāl-yən 

: relating, belonging, or owing allegiance to another country or government

alien

2 of 3 noun

: a foreign-born resident who has not been naturalized and is still a subject or citizen of a foreign country

illegal aliens

an alien lawfully admitted to the United States for permanent residence

—U.S. Code

alien

3 of 3 transitive verb

: alienate

Etymology

Adjective

Latin alienus not one's own, foreign