[ hahy-droh ]

noun,plural hy·dros for 2, 3.
  1. Informal. hydroelectric power.

  2. Informal. hydroplane.

  1. British.

    • a bathhouse, hotel, or resort catering to people taking mineral-water health cures; spa.

    • an establishment furnishing hydrotherapy.

  1. 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.

Other definitions for hydro- (2 of 3)


  1. a combining form meaning “water,” used in the formation of compound words: hydroplane; hydrogen.

Origin of hydro-

<Greek, combining form of hýdōr water
  • Also especially before a vowel, hydr-1.

Other definitions for hydro- (3 of 3)


  1. 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. 2023

How to use hydro in a sentence

British Dictionary definitions for hydro (1 of 4)


/ (ˈhaɪdrəʊ) /

nounplural -dros
  1. 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) /

  1. short for hydroelectric

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

British Dictionary definitions for Hydro (3 of 4)


/ (ˈhaɪdrəʊ) /

  1. (esp in Canada) a hydroelectric power company or board

British Dictionary definitions for hydro- (4 of 4)


combining form
  1. indicating or denoting water, liquid, or fluid: hydrolysis; hydrodynamics

  2. indicating the presence of hydrogen in a chemical compound: hydrochloric acid

  1. indicating a hydroid: hydrozoan

Origin of 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

Scientific definitions for hydro-


  1. 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.