Terrestrian adjective 1noun 1forms 3 adjective1 •Of or relating to Earth or its inhabitants; of terrestrial origin.In the meantime the Terrestrian and Venerian governments were already preparing vigorously for further inroads. — 1930 noun1 •An inhabitant of Earth; a human.This rocket squad was composed almost solely of Terrestrians, for they were used to the greater gravity of Earth, and could stand greater acceleration than could Venerians. — 1930 formsTerrestrians · more Terrestrian · most Terrestrian