ter·res·tri·al (t?-r?s?tr?-?l)adj.1. Of or relating to the earth or its inhabitants.2. Biology Living or growing on land or on or in the ground; not aquatic, arboreal, or epiphytic: terrestrial mammals; terrestrial apes; terrestrial orchids.3. Astronomy Similar to the planet earth in size or composition: terrestrial planets.4. Transmitted from structures on the earth and not involving satellites: terrestrial radio.5. Archaic Of or relating to the earth rather than heaven.n. An inhabitant of the earth.[Middle English, from Latin terrestris, from terra, earth; see ters- in Indo-European roots.]ter·res?tri·al·ly adv.ter·res?tri·al·ness n.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.terrestrial (t??r?str??l) adj1. of or relating to the earth2. of or belonging to the land as opposed to the sea or air3. (Biology) (of animals and plants) living or growing on the land4. earthly, worldly, or mundane5. (Broadcasting) (of television signals) sent over the earth’s surface from a transmitter on land, rather than by satellitenan inhabitant of the earth[C15: from Latin terrestris, from terra earth] ter?restrially adv ter?restrialness nCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014ter?res?tri?al (t??r?s tri ?l) adj. 1. pertaining to, consisting of, or representing the earth as distinct from other planets. 2. of or pertaining to land as distinct from water. 3. a. growing or living on land or on the ground; not aquatic, arboreal, etc. b. growing in the ground; not epiphytic or aerial. 4. of or pertaining to the earth or this world; worldly; mundane. n. 5. an inhabitant of the earth, esp. a human being. [1400?50; late Middle English