2. Prefix. (chemistry) hydrogen ¹
3. Prefix. (minerology) a hydrous compound ¹
4. Prefix. (zoology) Hydrozoa ¹
¹ Source: wiktionary.com
Medical Definition of Hydro-
1. Hydr- 1. Water, watery. 2. Containing or combined with hydrogen. 3. A hydatid. Origin: G. Hydor, water (05 Mar 2000)