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.
An inhabitant of the earth.
[Middle English, from Latin terrestris, from terra, earth; see ters- in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.