- 1alien (to somebody/something) strange and frightening; different from what you are used to synonym hostile an alien environment In a world that had suddenly become alien and dangerous, he was her only security.
- 2(often disapproving) from another country or society; foreign an alien culture alien influences that threatened their way of life
- 3 (disapproving) not usual or acceptable alien to somebody/something The idea is alien to our religion. A referendum is alien to the party's concept of democracy. Cruelty was alien to him.
- 4connected with creatures from another world alien beings from outer space