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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
Racial issuesRace and ethnicity
strange and not familiar: When I first went to New York, it all felt very alien to me.Unknown and unfamiliar [before noun] relating to creatures from another planet: an alien spacecraftStrange, suspicious and unnatural things and people

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.Racial issuesRace and ethnicity a creature from a different planetStrange, suspicious and unnatural things and people
(Definition of alien from the Cambridge Advanced Learners Dictionary & Thesaurus © Cambridge University Press)
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