—n. 1. Informal.hydroelectric power.
3. Brit. a. a bathhouse, hotel, or resort catering to people taking mineral-water health cures; spa.
b. an establishment furnishing hydrotherapy.
—adj. Informal.of, pertaining to, or furnishing water, water power, or hydroelectricity: funds for new hydro projects.
a combining form meaning “water,” used in the formation of compound words: hydroplane; hydrogen.Also,esp. before a vowel,hydr-1.
a combining form representing hydrogen in compound words, denoting esp. a combination of hydrogen with some negative element or radical: hydrobromic.Also,esp. before a vowel,hydr-2.