a·li·en (??l?-?n, ?l?y?n)adj.1. Owing political allegiance to another country or government; foreign: alien residents.2. Belonging to, characteristic of, or constituting another and very different place, society, or person; strange. See Synonyms at foreign.3. Dissimilar, inconsistent, or opposed, as in nature: emotions alien to her temperament.n. Law 1. An unnaturalized foreign resident of a country. Also called noncitizen.2. A person from another and very different family, people, or place.3. A person who is not included in a group; an outsider.4. A creature from outer space: science fiction about an invasion of aliens.5. Ecology An organism, especially a plant or animal, that occurs in or is naturalized in a region to which it is not native.tr.v. a·li·ened, a·li·en·ing, a·li·ens Law To transfer (property) to another; alienate.[Middle English, from Old French, from Latin ali?nus, from alius, other; see al- in Indo-European roots.]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.alien (?e?lj?n; ?e?l??n) n1. (Law) a person owing allegiance to a country other than that in which he lives; foreigner2. any being or thing foreign to the environment in which it now exists3. (Literary & Literary Critical Terms) (in science fiction) a being from another world, sometimes specifically an extraterrestrialadj4. unnaturalized; foreign5. having foreign allegiance: alien territory. 6. unfamiliar; strange: an alien quality in a work of art. 7. (and foll by: to) repugnant or opposed (to): war is alien to his philosophy. 8. (in science fiction) of or from another worldvb (Law) (tr) rare to transfer (property, etc) to another[C14: from Latin ali?nus foreign, from alius other] alienage nCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014al?ien (?e?l y?n, ?e? li ?n) n. 1. a foreign-born resident who has not been naturalized and who owes allegiance to another country. 2. a foreigner. 3. a person who has been estranged or excluded. 4. an extraterrestrial. adj. 5. owing allegiance to another country. 6. belonging or relating to aliens. 7. unlike one’s own; strange. 8. opposed; hostile (usu. fol. by to or from): ideas alien to modern thinking. 9. extraterrestrial. [1300?50; Middle English