1. Of, involving, moved by, or operated by a fluid, especially water, under pressure.
2. Able to set and harden under water, as Portland cement.
3. Of or relating to hydraulics.
[Latin hydraulicus, from Greek hudraulikos, from hudraulis, water organ : hudro-, hudr-, hydro- + aulos, pipe, flute.]
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.