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English definition of “alien”

alien

adjective uk   /ˈeɪ.li.ən/ us  
coming from a different country, race, or group: an alien culture
Synonym
strange and not familiar: When I first went to New York, it all felt very alien to me. [before noun] relating to creatures from another planet: an alien spacecraft

alien

noun [C] uk   /ˈeɪ.li.ən/ us  
specialized law someone who lives in a country of which they are not a legal citizen: When war broke out the government rounded up thousands of aliens and put them in temporary camps. a creature from a different planet
(Definition of alien from the Cambridge Advanced Learners Dictionary & Thesaurus © Cambridge University Press)
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