Hydro/ˈhaɪdrəʊ/ Definition 1 of 4Pro Tip 1/2Electricity Creation Understand 'hydro' as a place that uses water flow to generate electricity. The valley's hydro provides power to the nearby cities. Pro Tip 2/2Physical Structure 'Hydro' can refer to the power station building itself, not just the energy. The old hydro is a landmark and a monument to renewable energy.