MartianPronunciation: /ˈmɑːʃ(ə)n/Translate Martian | into Italian Definition of Martian adjective relating to the planet Mars or its supposed inhabitants: the Martian atmosphere the first Martian colony noun a hypothetical or fictional inhabitant of Mars: a nest of MartiansOrigin: late Middle English (in the senses 'subject to Mars's influence' and 'martial'): from Latin Mars, Mart- (see Mars) + -ianMartian in other Oxford dictionaries Definition of Martian in the US English dictionary