e·qua·to·ri·al (ē′kwə-tôrē-əl, ĕk′wə-)
a. Of, relating to, or resembling the earth's equator.
b. Relating to conditions that exist at the earth's equator: equatorial heat.
2. Being or having a mounting with two perpendicular axes, one of which is parallel to the earth's rotational axis, allowing a telescope so mounted to track a celestial object for long periods with adjustments only to that axis.
A telescope having an equatorial mounting.
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.