Hydraulic/haɪˈdrɔːlɪk/ Definition 1 of 3Pro Tip 1/3Mechanical Context Often used in contexts dealing with machinery or vehicles. The mechanic checked the car's hydraulic brakes. Pro Tip 2/3Tight Spaces 'Hydraulic' implies liquid pressure usage in confined areas. The hydraulic cylinder is used to move the lift. Pro Tip 3/3High Power Hydraulic systems can create strong movement or force. Hydraulic excavators can lift heavy boulders.