alien

adjective

• 1belonging to a foreign country:an alien culture
• (of a plant or animal species) introduced from another country and later naturalized: many food chains are based upon alien plants

• 2unfamiliar and disturbing or distasteful:principles that are alien to them they found the world of further education a little alien

• 3supposedly from another world; extraterrestrial:alien beings an alien spacecraft

noun

• 1a foreigner, especially one who is not a naturalized citizen of the country where he or she is living:an enemy alien
• a plant or animal species originally introduced from another country and later naturalized.

• 2a hypothetical or fictional being from another world: she discovers that the alien’s spaceship has crashed