[ hahy-droh ]
/ ˈhaɪ droʊ /

noun, plural hy·dros for 2, 3.

Informal. hydroelectric power.
Informal. hydroplane.
  1. a bathhouse, hotel, or resort catering to people taking mineral-water health cures; spa.
  2. an establishment furnishing hydrotherapy.


Informal. of, relating to, or furnishing water, water power, or hydroelectricity: funds for new hydro projects.

Origin of hydro

1880–85; by shortening of compounds with hydro-1 (cf. -o); (def 4) hydro-1 analyzed as an adj.

Definition for hydro (2 of 3)


a combining form meaning “water,” used in the formation of compound words: hydroplane; hydrogen.
Also especially before a vowel, hydr-1.

Origin of hydro-

< Greek, combining form of hýdōr water

Definition for hydro (3 of 3)


a combining form representing hydrogen in compound words, denoting especially a combination of hydrogen with some negative element or radical: hydrobromic.
Also especially before a vowel, hydr-2.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for hydro

British Dictionary definitions for hydro (1 of 4)

/ (ˈhaɪdrəʊ) /

noun plural -dros

British (esp formerly) a hotel or resort, often near a spa, offering facilities for hydropathic treatment

British Dictionary definitions for hydro (2 of 4)

/ (ˈhaɪdrəʊ) /


short for hydroelectric


a Canadian name for electricity when it is supplied to a residence, business, institution, etc

British Dictionary definitions for hydro (3 of 4)

/ (ˈhaɪdrəʊ) /


(esp in Canada) a hydroelectric power company or board

British Dictionary definitions for hydro (4 of 4)


sometimes before a vowel hydr-

combining form

indicating or denoting water, liquid, or fluidhydrolysis; hydrodynamics
indicating the presence of hydrogen in a chemical compoundhydrochloric acid
indicating a hydroidhydrozoan

Word Origin for hydro-

from Greek hudōr water
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medicine definitions for hydro



Water; liquid:hydrocephalus.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Science definitions for hydro


A prefix that means: “water” (as in hydroelectric) or “hydrogen,” (as in hydrochloride).
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.