Entry 2 senses · 2 variants Webster, 1913 Martian /märʹshən/ · Mar·tian · IPA /ˈmɑɹʃən/ prop. a. prop. n. 01 prop. a. Of or pertaining to Mars, the Roman god of war, or to the planet bearing his name; martial. 1. Of or pertaining to Mars, the Roman god of war, or to the planet bearing his name; martial. 02 prop. n. An inhabitant of the planet Mars; -- fictional or hypothetical. 1. An inhabitant of the planet Mars; -- fictional or hypothetical.