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

plural aliens

1

: extraterrestrial

a sci-fi movie about aliens visiting Earth

2

sometimes disparaging + offensive; see usage paragraph below

a

: an immigrant who has not been granted citizenship and is still a subject or citizen of a foreign country

broadly : a foreign-born resident

b

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

3

: exotic sense 1

kudzu, Russian thistle, and other aliens

Usage of Alien

Sense 2a of the noun alien still has use in U.S. immigration law and some other legal contexts, but in general use it is often regarded as offensive.

alien

3 of 3

verb

aliened; aliening; aliens

transitive verb

1

: alienate, estrange

2

: to transfer the title of (property)

Synonyms of alien

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

Sure looks to me like that whitetail along the edge of the frame is about to be alien poop. —Josh Honeycutt, Outdoor Life, 30 Oct. 2025

But any successful work of art or entertainment should feel genuine and relatable in its emotional scope, even if the circumstances are completely alien. —Kelly Lawler, USA Today, 30 Oct. 2025

Noun

As a girl, Smith had fantasized about being from a tribe of nomadic aliens or Native Americans. —Amy Weiss-Meyer, The Atlantic, 31 Oct. 2025

The theme for season 13 hasn't been unmasked, but prior seasons have tackled everything from a cult to a coven to aliens. —Lauren Huff, Entertainment Weekly, 31 Oct. 2025

Verb

On the other hand, this rebranding risks aliening White Castle's core customer groups. —Hugh Cameron, MSNBC Newsweek, 20 Oct. 2025

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

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 entry 1

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 2b

Verb

14th century, in the meaning defined at sense 1

Phrases Containing alien

• anti-alien
• 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